Dust Collection
Welcome to the gateway of Festool; first time i used a Festool Dust Extractor, I understood why the green kool-aid is so tasty.
I can't comment on the CT MIDI specifically, but I have two AC 36's and the CTL Sys (plug in, not battery powered).
I got the first 36AC because I also got the Planex for Drywall, and you REALLY REALLY need the AC (Auto-clean) feature, which uses a different filter, for Drywall. I have a second one because i got it for a song on craigslist, with the caveat it was used in a Marijuana grow operation, so it has an "odor" when you use it, if you know what I mean lol.
I got the Long Life bag for the CTL Sys vac; honestly, I wouldn't bother with those; you lose the convenience of being able to take the disposable (204308) bags to the trash and avoid dealing with dust.
As commented, a cyclone is nice, and makes your bags last a LOT longer. I have the Oneida one (Ultimate Dust Deputy Systainer Cyclone Separator Kit) and I also have the Festool CT-VA 20 Cyclone (204083). I'm always doing projects around the house, and i have Systainer drawer tool boxes, etc on top of my dust collectors, turning them into tool cabinets, which is awesome. The Oneida separator is better, but you lose the ability to put systainers on top of the Extractor; the Festool Cyclone you can still stack on top of it, although you can start getting a little ridiculous in height. My Oneida one just sits in the shop now, and the Festool one is always on one of my extractors.
Sanding
I have a bunch of Festool sanders; DTS 400 (577520), RTS 400 (576054), ETS EC 150/3 (576326), RO 150 (576028), Planex 2.0 575994 and the original Planex.
The one you listed, the ETS EC 150/5, is just a larger orbit pattern compared to the 150/3 I have; slightly more aggressive than mine, but I can say, the ETS EC 150/3 was my first Festool sander; what a game changer. So comfortable for those long sanding sessions. Wont turn on, by default, if Dust extraction isn't hooked up, comfortable, dust extraction is amazing, etc. I used a 5" Dewalt for years; the Festool was like another enlightening moment.
The DTS and RTS are def "less" amazing, but they have purposes; corners and narrower pieces is the reason i got them. I've use them on floors, doors, drywall, etc etc. BONUS: The sanding block (496962), hooks up to dust extraction, and uses the same paper as the RTS 400; I use it all the time for things like drywall touchups where it just needs a tiny bit of sanding, and no dust.
Domino
As other folks have said, I don't even think this needs justification. Absolute game changer. As a parent with two young kids, where shop time is super valuable, it saves so much time vs traditional Mortise/Tenon methods. You will find yourself using it cuz, why the hell not. I have been putting up new trim around Doors and Windows, and the 500, just for alignment, is fantastic.
Anyone who goes on about how it's "cheating" can go lick a frozen flag pole. I've had exactly zero people I've built something for say to me "omg, you cheated with Domino". I get it if you are doing through tenons for something traditional, but 99.999% of the time no one cares. Ive inter-mixed it with through tenons in a piece.
I have the 700; I got it, with the Seneca adaptor for 500 bits, thinking I can just use this for everything; Yeah, it works, but honestly, the 500 is what I reach for 98% of the time; I haven't used my 700 in a LONG time since getting the 500. Don't get me wrong, the 700 is great, making full size doors for example, but the 500 is definitely more bang for the buck.
I built a bunch of systainer cabinets using the Domino Connector Set (576797). I gotta say, its pretty friggin cool. I build them all out of Melamine ($50 a sheet at HD) and it worked great. It will allow me to break them all down in the future if I ever move, and take them with me. Only other system that competes with it from what I have seen is the Lamello stuff, but I don't do enough to justify the Lamello (remind me one day I said that...)
Tracksaw
I have the TSC 55 KEB (576717) and the TS 75 (576118).
The TSC 55 KEB is the one with the thinner blade. Its cordless, and fantastic. I use this 99% of the time. This, with the MFT's and STM 1800, breaking down sheet goods is a dream. Only comment I would make is yeah, the cordless thing is great, but I ALWAYS hook mine up to dust extraction anyways; so if it was corded? I don't think it would be that detrimental. The small bag that comes with it for dust works great, but fills up fast.
I bought the TS 75 with the same thoughts as the Domino 700; I can just use this for everything. The 75 is great, and i needed to cut some thicker stuff which came in handy, but I felt it was a little "off", and i know there are some threads on here about fixing that, but I honestly haven't used it in so long since getting the cordless 55, I haven't even looked at how to fiddle with that.
Router
I have em all; MFK 700, OF1010 (original one), OF1400 and OF2200.
If I had to only have one, it would be the OF1400. It has power for most tasks, can hook up to the LR32 system, great dust extraction, and can do all the shank sizes.
As far as use; lately i've used the MFK 700 the most; just so much easier to single hand for quick round overs, and I have the base for trimming edge banding from the Conturo. The MFK 700 would be my close second for must have router.
The 1010 is a great router, just not first on the "to have" list, since the 1400 can do everything it can (LR32 system). I got it for a good price is the only reason i have it, and basically just use it for LR32 and if on a project my 1400 is chucked up with a bit and setting i don't want to mess with.
I got my 2200 for a song as well; my buddy was buying another tool off Craigslist, and the guy had a brand new 2200, never used and accepted a good offer. He also included the systainer accessory kit with all the bases. I have literally not used it yet. This purchase was because the price he wanted was way too good to pass up AND I have an addiction.
I got all my routers from someone on Craigslist for crazy good prices. All of them were never even used, all but 2200 were in a Classic systainer. They looked like they were purchased circa 2009-11, and i came into possession in 2021. I can confirm that an unused Festool kept in it's systainer maintains that Fresh Brand new Festool smell (Yes, Festool gear has a smell)
Other Points
Bluetooth remote - You would have to pry them from my cold dead hands.
I just started using Granat on the Rotex (Still going through a big supply of Klingspor paper). Klingspor is good, but Granat, holy crap. I will be replenishing I think with Granat when the time comes. Having the papers in a systainer is really nice.
I don't have any Roll Boards, but I do have a Sys Roll (498660). I love it, easy to roll my tools around wherever i'm working, and you can kinda "pull" it up stairs, has this plastic bumper material in the back.
As stated above, I personally wouldn't bother with the Longlife Filter bag.
If First purchase is Sander and Dust extractor, def get the bluetooth remote, extra bags. As far as a sander, i know the Rotex 150 "can" do the random orbit sanding in one mode, other mode is "rip your face off" mode. It could fill the role of being a very aggressive sander and a finish sander (instead of the ETS EC 150/5). I have never used the Rotex for anything other than aggressive mode though. You are on the money though, Dust Extractor is key for all the other tools.