Has the rear DO spacing been determined yet? If 120, the rear spacing has to be spread. If 126, 7 will work. If the hub accepts a freewheel, then get a 7 speed freewheel and use the 7 speed STIs. Better option is to get a 7 speed rear freehub that works with shimano Hyperglide cassettes. Or your can get a 126 spaced Uniglide freehub and change the freehub body to one that accepts Hyperglide cassettes. You'll have access to the current cassette products made for Hyperglide hubs.