You lucky dog.
With the size and sharing constraints you have, I'd do it like this.
Put a 9' OH door at the far end 2' from the outside wall on the 32' side.
Put another one 16" from that one. Separate them with a partition. Put a 3'
pocket door in the partition 6' from the wall at the back of the garage. Now
SWMBO has a dedicated parking place and room at the back for storage. For
Xmas decorations, switch to Islam. For all the rest of the crap that
collects in a family, put a dumpster enclosure outside.
Now, for your 2/3's of the space. I wouldn't paint the concrete. I'd use a
shake-on color/hardener when the slab is poured. It is shaken on and mixed
into the mud on the surface with the float machine. It's about 1/4" thick
when finished and wears like iron because it has iron in it.There is no
dust. A sealer protects against stains and can be renewed, but probably wont
have to be in our lifetimes of home use. The color wont chip peel crack or
fade, it's part of the concrete. Pick a color you like. I like white or
light gray. There is a large range of these available. Talk to your concrete
contractor. If you do the slab yourself with some buddies, get at least two
who do flatwork for a living to run the show, and know what to do. Once the
mud is poured you don't have time to scratch your head, mistakes made on the
slab are expensive to correct.
I would probably frame the whole thing with steel studs joists and rafters.
Make it as tall as codes and architectural aesthetics will allow. If you
can, make your OH door 10' high. Firerock on the inside walls. 1/4" tempered
hardboard 4' up to protect walls. Lots of 120 VAC outlets 4' high on
walls.Copper air lines inside the walls 6' high with a sub out every 8' or
so. 3 phase loop around the room 5' high with a 4x4 box every 8'. Ceiling
outlets near the OH door and in the middle of the room. Air lines at those
locations also.
OSB sheathing on the outside. Finish O/S to suit home. Separate little room
outside the building behind the dumpster enc. for mechanicals, central vac,
3 phase converter. H2O heater, beer cooler etc. zoned hydronic heat, lots of
light fixtures.
Thanks for the opportunity to fantasize.
Tom.
PS Put sign on the door "NO GIRLS ALLOWED"