I'm going to try to stray from repeating the more common suggestions, but some I feel should be reiterated
Lag - Every match is a completely different experience from the next unless you are the host. I think if you made the person with the lowest bandwidth host it may compensate for the lag since it's usually a geographical issue and not so much a bandwidth one in most cases. This would decrease the host advantage and increase responsiveness.(Even though in some cases that means a bad connection and lag from geographical location). For the most part it would level the playing field since the higher bandwidth players have to stretch theirs(bandwidth) instead of the lower ones stretching theirs. With the rich content and rendering involved in a game like gears you get bullet lag very badly when you play a high bandwidth host far away, even with a solid connection.
Bringing back the connection error from the first gears so we could quit a match with a bad host and not be penalised and also eliminate the stand byers would be great.
MP Gameplay Bugs - The vacuum for the chainsaw and other melees is still a problem.
When any explosion from a boomshot, torque, grenade, etc, is too far away to affect you and a teamate is between you and the explosion they act as an entirely new one. Instead of shielding you from damage they multiply it. Which is frustrating when you're playing with someone who loves to walk ahead and set off proximity grenades.
Also smoke grenades can glitch you through security gates unscathed. They can still send you down or up levels where you would not normally be able to go on multiple maps. Like the torque and longshot spawns on river for example.
MP Gameplay Suggestions - A free for all game type would be amazing. I understand that you don't want to destroy the integrity of the game but you don't want to stick yourself in a box either. Before an update on the first Gears you had to wait for the round to be over to respawn then annex happened and you tore a few walls down. It'd be great if you could do that again, I know you want it to be Cogs Vs Locust( but who cares you can already be 5 Marcus Fenixs against 5 Raams in a match and I don't think you had cloning in the campaign story so ****it let us kill each other and not depend on a team.
I know this has been said a million times since Gears 2 was released but it has to be done sooner or later...CUSTOM MATCHES. I want to be able to see the host connection again and I want to be able to pick my game type and map. I don't like having to play the same map three times in a row with the same game type I hate because of other people, I want my own choice.
I would love to see the melee damage go down to three hits and the shotgun damage to go up. If someone has to reload in close combat with a shotgun they should die buck shot hurts more than a baseball bat.
Thank you for an amazing game that you continue to improve and develope for your fans, because we know you're just as big of fans as we are