Matt's stove is awesome, but I don't know about how much space it will heat. I thought it was designed for a smaller space than 900sf, but I could be wrong. If we are lucky Matt will see this post and comment.
I built a batch stove of Peter's design--heats 800-900sf between 62-72 for 24 hours on a single load of scrap 1x4 pine I have for free. Since it is a workshop I suggest the batch load stove since you want to actually get work done and not tend a J style rocket. It is so easy to load of the batch and have heat lasting all day and into the morning.
Barrel is long lasting. I think Ianto has a rocket he built that is 20+ years old and still in use.
As for looking to the vertical instead of a horizontal bench, just consider doing a larger vertical masonry bell--could be cob or brick or something else, just build up instead of out.
Check out the applications section of Peter's website here http://batchrocket.eu/en/applications
. He has a pretty vertical heater in his shop that might do the trick.