I'll throw that out in the Executive Committee meeting this weekend, Greg. The rules are set up to follow current rules in WSBK's new lightweight class, but it doesn't consider "obsolete" models.
As long as there is no competitive advantage that breaks the rules I think it'll be OK. EX500 makes right on 50 hp, so that's a little more than CBR500R (47) and markedly more than KTM RC390 (43) or Ninja 300 (39) or R3 (42). That said, it's also a bit heavier (like the CBR500R) so I think as long as the prep rules are adhered to it'll work out fine.
I'll post again after the meeting on Sunday.