Short-term (5ish year) Studio Build

Not sure if this is the appropriate spot, but:

I've been debating building a short-ish term studio space (just composing on keyboard and DI guitars with a DAW). The concrete pad is only 8.5x12ft. Any larger and I have to get the city involved, add concrete, get permits, etc, taking this probably well into 5 figures. Would like this to be repurposed down the road into storage or an art studio space, etc.

I was initially unsure about this, but have decided I don't want a long-term outdoor studio space anyways, since I'd rather have it our future house build for added security. That said, I need somewhere to create in the interim. Have about 2 acres so space isn't the issue but development cost is.

Are there any design considerations to include? Is this a bad idea? I'd like to keep it lower cost, so I was thinking a shed roof slanted lengthwise up and away from the control desk area.

Also not sure what to do with windows. Airflow is obviously mandatory, but I'm not sure what kind of windows to include or whether to include them. Also a security risk and a sound leak area, but a dark room might be a bit difficult and stifling in the summer. Small windows up high? A skylight?

My current plan is:
-2x6" studs -- is 2x4" better for a minute amount of square footage? Already have a pile of 2x6 studs
-Rockwool insulation
-Shed roof slanting from 10' to 8' lengthwise (sloping down 12') -- I'm thinking a slanted ceiling will break up the symmetry and also provide more volume
-No windows, or possibly a small one
-Seal all airgaps