I'd love for the project to have a proper front-end so that it made everything easier to configure from control setup to the addition of games. Add, Organize, Launch... PLAY! Simple as that.
Some might know my involvement with the OpenEmu project and what is planned for that.
I would sorely love MAME to be an included 'core' for that project. The thing is, it is so badly coded now (or confusingly coded) with tons of hacks and revisions, that it would be a mammoth project in itself trying to integrate it properly.
These front-ends we have currently for MAME are nice but, ultimately frustrating and confusing for people.
A true layman's guide to it all would be a nice undertaking for the community.