Weighting of H3 BR/AR starts in social 4v4 is definitely NOT 50/50. I’m constantly getting thrusted into matches where it is AR starts at least 75% of the time and on a map like Snowbound or Heretic it is ludicrous. I would be all for even cutting it back all the way to ONLY BR starts. From what I’m aware H2C social 4v4 is strictly BR starts, so making H3 the same wouldn’t be that unreasonable. There are simply too many maps that don’t play well under AR starts to make the weighting as high as it is. I’ve seen many others on here complaining about it so I know I’m definitely not alone in this opinion...
Additionally, I’m having TONS of issues with blank melees in both H2C and H3. I’m losing many close quarters battles because meless aren’t registering and occasionally the animation won’t even happen. I thought perhaps it was my controller so I switched to two other controllers and have experienced the issues on both of them as well. This particular issue is exclusive to Halo 3, in Halo 2 the animation will always show up but melees don’t always register (which has been an ongoing issue for H2C since MCC’s release). But the H3 melees seem to have gotten worse, whereas before the last update I don’t remember having hardly any problems with them. Not sure what’s going on here but this should be addressed.
I'm probably in the minority that prefers the original starting weapons (SMG on H2, AR on H3, etc) on a lot of the smaller maps rather than BR starts on everything; but along similar lines as your comment, some of the games are completely changed and more or less spoiled by BR starts, particularly in H2C.
Example: The map "Midship" in original H2 was always such a glorious and refreshing change of pace because it was different. You had to get creative with duals/grenades/melees since everyone started with a plasma rifle, and a big part of the game was controlling the map and the power weapons with your team. Now it's just spawn and instantly shoot across the map with the BR, and the power weapons lose most of their value since a BR can easily take out a sword/shotgun unless it's close quarters. Simply put, it's a completely different game than that map was originally designed to be.
Suggestion for improvement would be to look at each map individually and determine what starting weapons make the most sense, instead of throwing a 'one size fits all' blanket over all maps. As stated in the quoted post above, BRs are 100% necessary on some maps, particularly the mid to large sized maps...but some of the smaller maps lose much of their fun with BR starts.