More power to you it you can get it going.
I don't only see problems with the monitor and CPU but the microswitches also and Joysticks, moving objsects will be hard to seal around. You can cover them up to keep direct rain off, but a very wet day 100% moisture in the air will get everything wet inside if there is any outside ventilation.
I know this is a compromise, but I would make a sort of bar top with 4 handles on top to help 4 guys take it outside. If you want make a base to stay outside that it can sit on to get to the right height with a plug right there, keep the bartop inside except for parties.
Take some weight out to help, but most of a cabs weight is 3/4" MDF, bartop takes more than half the weight out. when the guys comeover have the first couple help you carry it out. Get creative and make it somewhat lighter, with a good way to lock it down.
A compromise, but I would hate to see a project end up a home for mice and wasps.