Sorry but please don't. Shooting games... not MMOs where everyone designs their persona.
Oh and also, they make those achievements hard because they want people to make it feel as if they are getting things out of hard work and it adds to the replay value (For example, people wouldn't play the campaign again on legendary after they beat it.)
As for things I would like to see:
Keep maps as it is... why ask for bigger maps when skirmishes are barely noticeable in maps like the new bloodguch?
Make veichle system back to Halo 3, DMRs and one sniper can take out a tank and hogs (banshees are madness also in this game with their crazy power) when they are supposed to do good against infantry and besides there are so many other ways to take out a veichle.
I do agree on some armour effects with some atachments to it.
AAs are out of the question, just take them out please.
I am fine with reach but just the feeling of vehicles, AAs and OP Banshees really take out the fun aswell as some maps being a bit too big for "HALO".
EDIT: I would also like to state because of the addition to soooo many playlists custom games are like nowhere to be found and people do not make them anymore so creativity will and would only be noticed if they become popular and come to appear on the hot-things category on a section and people can download it.
An example: Zombies, people made Custom Games for zombie matches because there was no playlist back then in halo 3 and if there was it was only for a few moments.
One last thing I would like to complaint. 4 people in local can't join into a big team battle? Actually, more than 2! Each day I keep thinking those extra 2 controllers I bought just were not worth it.