"Epic" is not what I want to see in a new D&D movie. They tried that; it does not seem to have worked out thus far.
Gritty should be the order of the day. Claustrophobic, dark, though not bleak. More "overgrown" .
I think Buried should be required watching for anyone making a D&D film. That film is an object lesson in doing more with less and the importance of light.
Anyway... Right now my personal choices for the make-up of the party would be a hard drinking female human fighter with a more barbarian aesthetic, a sensible male dwarven rogue/spelunker, a female elven wizard/fighter modeled on the old elf class, and a male cleric that focuses a bit more on the magic rather than the martial. Some inspirations would be Etoh for the clerc, Deedlit for the elf, Bronn (but nicer) for the dwarf, and Siege Girl/Farmer/Lady Montbarron for the fighter.