I've already done alright, it's got double doors high enough for a camper van, and a loft, and a beer fridge (and cupboard).
Alas I've filled it with stuff, the bike store, lathe, tools (so many tools), a climbing wall, the old kitchen units, several workbenches, ham radio equipment.
I'd really like some more woodworking tools, a planner thicknesser, and a table saw (I borrow my dads portable one), but I've got to keep some room for my dads 3 axis milling machine, 3 phase pillar drill and snap on boxes, when he gets to the age that it's time for them to move on.
I think I'd like a workshop extension.