PDGA LEGAL: Yes.
GLIDE: Medium to High, for "Lid-ness"
NEUTRALITY: Neutral or low LSS, high HSS stable
DIAMETER: I wouldn't mind up to a 22 cm to help fill the niche that the Gopher and similar lids filled of a wider diameter lid. I'd wait and see how people like the flight of the Beetle to give a clue.
RIM DEPTH: Polecat is perfect for me but I can go shallower.
SHOULDER: Prefer squared off.
THUMTRAC: I'm piqued by the idea of a RDG groove on a lid. It would be good to have something that would prevent clovering (a good plastic like Fossil will probably prevent this but throwing it out there). I really do not want to kill glide though. I think the RDG groove might not hurt glide too much if the disc has mild dome, the RDG and Element putters I've seen are all board flat and a contributor to lack of glide I think.
RINGS OF HEDRICK: I like them but if they damage the structural integrity of the flight plate like Sonics I say screw them. What would happen if you went radial spokes instead? If it's a Troll Cat it's got to have some cheeky feature, right?
RAISED CENTER: Nah, I'd say keep it uniform like a conventional golf disc.
DOME: Flat to mild dome.
OVERMOLD: I'm assuming the traditional route will be cheaper and easier. I think there are two "dream" lids in my mind, a wider diameter Pole Cat in sweet baseline plastic (this seems right in RDG's wheelhouse so this Troll Cat is reflected in my answers) but if a premium plastic, overmolded lid is pursued, I think an overmolded fastback would be elfballs and really novel, perfect marriage of old school and new school.
RIM "BEAD" RADIUS: Blunt, I hate sharp rims that scrape my fan grip.
BEVELED EDGE: Only the slightest bevel, prefer flat.
INTERNAL RIM TO FLIGHTPLATE TRANSITION RADIUS: Feel-wise, I prefer more squared. I do like the Ion's internal rim and wouldn't mind it, might help add a little gyro effect to it but I think squared off would be more popular.
PLUS RIM: HATE plus rims
WEIGHTS: My ideal lid weight is ~160-165g. I like light enough to be liddish but heavy enough that it's not a dramatic departure from 175+ mids and drivers. You can go as light as you like, especially if it helps change up the stability to give player's options.
Random idea: Can we put two "rings of Headrick", one each alongside of a groove? What the heck would that do?
Random idea #2: Polecat with a bead? Has it ever been done putting a bead on a lid?