How about the original barrel length, with a permanently attached flash hiding QD suppressor adapter that works with one of the flush mount suppressors available.

IE: Something like an AAC Blackout adapter that works with a can capable of mounting on the TAVOR like the SCAR-SD*.

Truth be told, the 16" would save everyone lots of headaches though.



*I have absolutely no experience with the TAVOR or the SCAR-SD, I just listed the SCAR-SD as it looks to be one of the suppressors capable of mounting on the IWI with it's minimal muzzle to hand guard clearance. The Surefire K series may also fit the bill as well.