Hi ...
Not sure about the TF series as I did not see any midi capability or control emulation mentioned for this series. It does indicate control over ethernet but I am not convinced that this means DAW control in addition to IPAD control. With that said.. I have seen your fantasy come pretty close with my current setup(s). These consist of the A&H QU 24 and the Zed R16. The QU is closer to what you are looking for due to its motorized faders. This combined with Azslow3's Sonar tool, It controls the surface very nicely. Giving more capability than just the standard midi fanfare. From faders, volume, mutes, solo's to bank switching and buss control, it is all there. I am very happy with the setup. I have done the same with his tool for my Zed R16.. Do a search on the forum for "you can control your daw as deep as you like". I believe you will be pleasantly surprised and maybe even "fantasyfied"..
In regard to it being a good idea.. This has been done in some form or fashion for a long time.. Digidesign, Tascam, Roland, Cakewalk and many others have combined interfaces and controllers for awhile. Even on the higher end consoles API , SSL and Neve come to mind, this is done. So it is not uncommon.. My two pence....IHTH