It was an interesting thought experiment for about 2 1/2 seconds until cynicism/skepticism kicked in.. the list of amendments on said law would likely look something like this:
1) Rifle loony lobby would attach wording to allow same, but only with the cartridge of their choosing.
2) Anti's would limit law to spring powered single shot bean bag guns only, with an orange tip and no "thing that goes up" on the stock
3) The critter huggers would want velcro tipped foam bullets, so no animals would be harmed.
4) The tree huggers would throw in with the critter huggers as long as said bullets were non carcinogenic, bio-degradible and/or edible, and preferably made from recycled materials.
5) .gov would undoubtedly put a nice safe speed limit on them of around 140-180 FPS. In lieu of the now unnecessary tax stamp for suppressors, the will allow the new option of foam wrapping and velcro coating a rock of less than 16 oz., as long a you fill out the necessary paperwork, go through the waiting period,have a serial number on said rock, and buy a tax stamp for $500. No collecting surplus rocks from federal land either (they're not in that business anymore you know, and ABSOLUTELY no green tipped rocks)
6) Dry firing is mandatory and must be documented by a fed. certified instructor who will issue a certificate for a "reasonable" fee.

Cynicism toggle off. smile

I need another cup of coffee.

While I don't disagree with the premise of more practice, and do you really truly need more than one rifle to do the job on the vast majority of big game at least in N.A. (no, not really), any kind of "law" only opens things up to people who know how to manipulate them, and only restricts those who do know squat about the subject.
On to the next topic... If we all had only XXX vehicle to drive, could only use regular or mid grade, and practiced a lot..in our driveway...we'd all be better drivers smile