You will definitely need to take the drywall down if it's right on the Block and then and frame the walls...That will be horrible once you have snakes in there!

If you insulate the room well (use a very high rating) you shouldn't need extra room heat too often...Oil Filled style heaters are very expensive to operate and suck the humidity out of the room...You should look into this type of heater if you do need to run one...
http://edenpureus.us/?gclid=CPbgpMDh4q8CFUhl7AodanGgEg

I would add fluorescent lights for when you are in there...No need to run them when your not in there if you don't want to...They don't need a light cycle.

You will need to address the humidity issues as you cross that bridge...It's hard to say what it will be like until you get everything in there...

I would also look into a really good air purifier so you don't have stale air sitting in the room...I like Oreck, but there are plenty of others...Just make sure you get one with washable filters, or that will get expensive.
http://www.oreck.com/Air-Purifiers?k...FQif7QodtVNRzg