ideally, just something that works with daphne's arcade controls and has access to all of daphne's setup options, similar to daphneloader, but that looks good on an arcade monitor and can be controlled without a keyboard/mouse.
All the fe's I've played with and investigated (which admittedly is not all of them) are primarily focused on mame, with daphne as an afterthought. Typically in these mame-focused frontends, daphne's options can only be set via command line. Frontends that do have access to all of daphne's options in the gui are typically written for daphne, like daphneloader, dirk, and daphnex's fe but they either aren't written with arcade cabinets in mind (Daphneloader and Dirk) or are buggy and outdated (Daphnex, Dirk). Plus, I've always wanted to see a daphne fe that was aware of daphne's methods, such as framefiles, and therefore could cycle attract modes, death scenes, etc, straight from the game's own m2v/ogg.
I'd even envisioned an fe specifically for cabinet users with LD players. You could do a frame seek to detect which disc was inserted, then cycle the attract mode (or other scenes) while displaying options and choices *specific to the game corresponding to the disc inserted* via a text overlay. Although I doubt this would ever happen, I always pictured the ideal daphne cabinet fe starting out this way for real LD players, and then evolving to use m2v/ogg- just like daphne itself did. You could build on the same fe, but add an eject and insertion of the virtual "laserdiscs". You could even build a "jukebox" that inserts different virtual laserdiscs and plays their different attract modes when no one is playing. Then when a user steps up to the machine, they can play the game the fe is currently cycling on, or change the laserdisc and select the game they want via the "jukebox". But yeah, pipe dream, I know.