Holey rail, as others have stated: get in with the saw for free so you have it should you ever go for a LR32, no downsides here.
CT Vaccum: A router will make lots of chips quickly (as you remove plenty of material in a short time) so a bigger vac makes sense (or add a cyclone infront to save on bags, but that's not supported by Festool). You don't want to run a router or the TS without a vac when working on MDF (as it's a mess and quite unhealthy), plus you can't with the Domino (as it would destroy the tool, or at least the cutter).
Should you decide on a MFT/3: look at the topics here regarding setting it up the first time (before you do a cut into the surface), it might not be perfectly square out of the box.
Also keep in mind that you'll need clamps (Bessey Revo KVR are nice for building boxes) and stuff, also some material to play with your new tools before you let them loose on expensive material (where you get the quantity you need and not 50+% more to destroy in experiments) obtained for a special project...