A few things:
You layout would likely work fine as long as you didnt angle the joysticks. The button placement woudln't be a big deal IMO and could work fairly well.
If you just *HAD* to have a trackball and wanted a straight button layout, you could grind away an area of the trackball plate for some more room. Someone did that previously and it worked fine.
If you don't think you'll play many trackball games, don't wast the time, money, and CP space. For me, I have a number of Windows games that I *need* on my machine and love the old trackball games, so no trackball is not an option for me.
1) Mouse within windows
2) PC games that use trackball (Tiger woods, hamsterball, etc etc)
3) Marble Madness
4) Missile Command
That's enough reason for me right there. if you don't care about any of that, don't bother, your CP will look cleaner.
Also, you mention "4/8 way Supers" Be aware that IMO (and the opinions of many others) that the Super is a pretty bad 4way joystick, and swapping them to 4way is not easy. If you really want a 4/8 way setup, either get a joy that is a better 4way in 4way mode, is more easily swappable, or have 2 seperate joys. Just my .02, but I can't stand Supers in 4way. Get a Ms. Pac Reunion stick which is based on teh Super but much better.