Pretty much what I was going to do - either a street ell or an ell with a close nipple to point the thing down, a brass/stainless ball valve, and put a hose barb fitting on it so I can direct the drain into a container somewhere.
A brass-bodied ball valve with a CRES (stainless) ball will work - the PTFE wipes shouldn't have any trouble at all, and the thing won't seize with heat or time (when I replace service valve or hose spigots in houses, I use ball valves for those as well. Same reason. For hose spigots, I just put a ball valve on and then put a hose bibb adapter on it after.
(That way, I don't have to deal with packing leaks, washer leaks, valves that don't turn fully, and if I need it on or off in a hurry, I can do that. One-quarter turn get all or none of the water - problem solved.)