Cortes,
I have a similar setup, but don't believe that I would hook up any of my Festools to the Oneida dust collector. It sounds like a good idea, but if you intend to use the dust collector with tools like the sander, domino, track saw, and probably others, I believe you would not get the same results that you would with a Festool vac (probably not the same results as you would get with a Fein or possibly others either). The purpose of dust collector is to move a large volume of air but I've found the suction is not as great. For tools like a jointer, planer, or a large cabinet saw, the dust collector is the best choice, but for smaller tools you probably would do better getting the higher suction that you get moving air through a smaller opening like the vacuum. I have had an Oneida central cyclone with an internal filter for many years (one of their first ones). It absolutely works great for my planer and jointer (and table saw when I used it). For any of my smaller tools and the Festools I have purchased (TS55, ETS125, Domino 500) I get the best results using the Festool vac (and before that my Fein). It is possible you could good results reducing to the Festool hose size, but I have never found that to be true (although never tried it on Festools). You may already know all of this and, if so, I'm sorry and didn't mean to indicate you didn't.