Alex,
I've had the TS55 with 2, 55" rails and a MFT 1080 (now MFT3) since 2005. You can do 95+% of what you need to do with that set-up without a tablesaw and without a mitersaw. It can be done safely and with close to 99% of the dust captured. On top of the safety and top quality cut you will have a tool that will last and hold most of its value should you need to sell it. Sheetgoods and regular lumber up to 2 1/8"(TS-55) thick are no problem. There are work arounds for the repeatable rip issue mentioned above
www.festoolownersgroup.com and if you don't want/can't afford an MFT you can DIY a table like Matt did easily and cheap
http://ncwoodworker.net/forums/showthread.php?t=37455 to do crosscuts, repeatable rips and do your dados with a router like a lot of us of us do.
Do you need a Festool TS-55? No Any Circular saw can be used in a Plywood saw guide. The Festool TS-55 is a different animal and part of a system.
Will a tablesaw make life easier to do some cuts? Yes There are work arounds for the plunge saw limitations if you look.
Do you need a SawStop with a Festool TS-55? No
Do you need to worry about kick back with a TS-55? No
Can you sit a cup of coffee on your TS-55? No
Can your Tablesaw fit in a Systanier 3? No
Like Bas, my best advice is get the TS-55, a tablesaw and an MFT3. My second best advice is get a good circular saw and a plywood guide to break down sheetgoods into manageble sizes and then use a tablesaw to get a final dimension. If you need just one tool with the limitations you mentioned, the TS-55, some guiderails and some type of table will work fine.