I know I'm not the first to ask about this, and I don't know if the limits are for technical reasons, but the ability to have multiplayer groups of more than 4 players would be nice. The custom game availability while cool can be overly deep and the loss of XP, equipment et cetera is disappointing. The inability to customize multiplayer games frankly is a bit baffling. For example, playing with a group of 6 friends it would be nice to play 3 vs 3 with or without AI supplements (or 4 vs 2 for that matter). If it meant a loss of contribution to the Faction War because that is tied to the outcome I'd wager you'd find that acceptable to people I've seen voice the same desire. For those of us in this boat it is definitely more important to us to be able to play with our larger group of friends while still being able to advance our heroes.
Thanks for your consideration
I think that wouldn't be helpful with the already small player base: options like this would mean that those who don't want to play with your settings would go into a different "bucket" (or waiting queue). Each of the possibilities/settings added (eg. "Dominion with no AI fill", "Dominion with AI fill") would split the current game modes (buckets) into even more buckets, leading to increased wait times for matches (not that they're so small) - potentially doubling them with every added setting. That is why matchmade games have settings (including respawn time and such) locked to some "sensible" defaults, which you can override in custom games, but since they can radically change games (and can potentially lead to very quick/long dominion/breach games), it might be possible to exploit them to quickly acquire steel or loot - that's why you get none of them in a custom match. Not to mention you fill up your team and/or your enemies the way you like, allowing for further bias in those matches.