I usually get shot down on things like this...but I prefer rambling, unique structures over brand new big boxes.
Were it me, I'd pour a 4" floor, build a back wall & frame the front wall & install overhead garage doors on the front.
Actually, your builder just bought the cheapest Clopay so he could say it's a Clopay door....I've had my 4 Clopay's up for over 15 years with no issues - but I bought high quality ones!
I'm with you e-tek....my wife went out & bought 2 Pier I captain's chairs for my garage TV! That's what she thought would be nice in a garage.....she's happy, I'm happy!
I left a wall of OSB in the open for a year & the OSB was still good when I started to cover it....however, on the roof, just roll some 30lb black felt over it.
Old cabinets from an apartment complex that was remodeling.....$5 for each one! Most, I've taken the doors off:
& since those photos were made, I've added these lights from Hobby Lobby all around the cabinets....found them on sale for $10.00: