You're completely missing the point.
Once again, in IDPA you won't be using your carbine in a low-light stage. You don't need it for IDPA, period.
So then Saigas would completely dominate, even though they are less than 5% of the market. If any one gun completely dominates a certain class, then you've got a broken competition.
Then you don't understand the point of IDPA or where it came from.
How much does it cost to buy a competitive gun for IPSC unlimited? $3000? That's what IDPA is trying to prevent. At one time, IPSC started with average guns. Before too long, however, it turned into an equipment race and if you want to be competitive in IPSC unlimited, you need one of these:
How many folks are carrying something like that or have something like that in your safe?
IDPA wants your average gun owner to be able afford to compete, and not to have to spend $3000 buying one of these two guns and add those twelve widgets in order to be competitive.
If you want to be able to use anything you want on your gun, you can do that -- IPSC unlimited is awaiting your entry.
Like Supermofo said, you don't need the open gun to be competitive in USPSA. I shoot the same gun and rig in IDPA as I do in Production division (well, slightly different holster in USPSA...but everything else is the same). Same with most other shooters who cross over between sports.
If you want to lay down the coin to play with the loud guns in open...go for it (it's addictive ), but it's not a requirement.