I'm a newbie to big matches, but I have the following observations of human nature:
0. If it's scored, timed, and prizes are given, it's a competition. People want to win.
1. If it's a competition, some people are going to spend a lot of money on their equipment to give them whatever edge they can. For example, you can shoot Limited class in IPSC with a Glock 22 and beat just about everyone if you're good enough -- but people still spend $2500 on a STI/SVI. A $3k rifle? Heck, you buy a DSA FAL or "Match" M1A and some good optics, and you're already to about $2500.
2. Corollary: If it's a competition, some people will limit their equipment and performance behavior by mainly what the rules define. (A good example of this might be the 50% (?) cover rule in IDPA.) Or it might mean having "untactical" mag holders that only leave exposed 2" of your mags.
The following might be a naive suggestion, but instead of setting more rules to attempt to make equipment "tactical, really", why not just design the match and stages to weed out those weapons that are not "battleworthy" ? That's the test of practicability - if it works, use it; it is breaks or doesn't work, lose it.
For example, if we're already in a 3Gun match, shooting a multi-gun stage, there's not much point in having a truly concealable pistol. In other words, if I'm supposed to be pretending I'm in a scenario with 40+ rounds required and I just happened to have my rifle and/or shotgun handy, I don't think it's much of a stretch to think I'd want to have my high-capacity 9x19, 40, 10mm, or .45 on me instead of my Glock 27. Certainly if I knew I was going to be entering some sort of SHTF scenario with 20+ zombies, I'd take the highest capacity pistol I could shoot fast & accurately with, but only if I knew it was totally reliable. For example, if an objection is that "race guns" are too sensitive to dirt, have us crawl around in the dirt on a stage. At Raton, everything including the insides of my clothes, shoes, holsters, car, and, yes, guns was coated in fine red dust by the end of the weekend
The rifles from JP which were legal for WC3Gun or RM3G (or basically any other "Tactical" rifle division) are not fundamentally different than your standard AR. In their top-of-the-line "CTR-02" model ($2100), there are a few design tweaks, e.g. to allow for mounting an ACOG directly to the upper receiver, but it is essentially an AR-15. Same stock, bolt design, gas system, free float tube, etc.
Sorry this turned out kind of ranty - I guess I'm not really sure what the objection was.
best,
Zak
[edit] And just for the record, I shoot an off the shelf single-stack .45, a stock Benelli, and a Rock River AR-15.