Are the clients you're talking with aware of the real issues with outdoor monitors?
If you search for outdoor display panels you'll notice there's a wide range of options - all a lot more expensive than the domestic offerings! Varying from fully enclosed/weatherproof through to simply brighter displays for daytime outside viewing.
I'd be more inclined to go for projection in my own application simply for simplicity and the fact that I'd rarely want to strain my eyes watching a panel in daylight!
Anyway, back to your actual question, as long as your cabinet is moisture proof and nothing electrical can get wet and short you should be fine. You may want a switch on the doors as heat build up could be a disaster if the unit is left on with everything closed up.
I'd probably insulate the inside of the cabinet to reflect heat and install a downward facing fan if I was concerned.
