Even if it could (I genuinely don't know, though I always thought that 9x21 was simply a lengthened 9x19 for easy compliance with laws in places like Italy) it sounds like an awful lot of work to end up with what is very cheap brass; I've seen once fired 9x19 go for about £35 posted/500.
Probably worth poking about EU sites, with the very weak Euro and much stronger pistol shooting scene over there you'll pick some up for not a lot.