I've been fairly curious quite how much you can mask the inherent weaknesses of a speaker or a room with an EQ curve. Steve rated the JBLs from the rooftops at how much difference they made.
But whats stopping you taking a midrange hifi cabinet, and just tweaking it into a machine of precision excellence through the simple overlaying of a compensatinv EQ setting?
I looked at soundsystem design for ages. Building big rig speakers isn't that difficult if you are a half decent cabinet maker and can follow insructions.
This guy is dead good - Rog Mogale:
http://www.speakerplans.com
Some lovely plans for big PA speakers. Mate of ours down in brighton has loads of "loony bins" and they siiiiiing. Beautiful precise warm bass, just a joy to listen to. Rate them much higher than F1 stuff personally. More character and less fussy.
There's probably some advantages of producing on a well set up engineered PA rig. You'll no doubt make tracks that tick all the boxes in a club, but might lack the detail you need to provide for the headphone listening crew.
Good luck anyways mate, you've set yourself a real challenge and sure you'll have fun and learn a stinkload.