I think you'll be ok, as others have said in different posts, you may need to add some Nitrogen. I would not just go adding lime or dolomite though. You should probably get a soil test done first to see what if anything you need to add to the soil. Check with your local university's agriculture dept, they often will do soil tests for low cost. I would also not worry about the fungus from the decaying wood, that will most likely help rather than harm anything.

Remove the middle, drill the drainage hole, soak the stump insides in a waterproofing substance (linseed oil, oil/beeswax. commercial stuff like Thompson's ... whatever. Put it on small feet to keep it off the ground. Instead of planting directly in the stump, use it as a "cache pot" for plastic pots. If the bark starts peeling, remove it and glue it on with wood glue and clamps.

When we had to cut down our big old Arizona ash last summer and I wanted to keep the stump high to put a bird house and planter on I gave the top several coats of black roofing sealer in hopes that it would stave off its rotting. It got just maybe a half dozen sprouts at the top and only two or three at the bottom all of which were twisted off instead of cutting them. I don't know if the tarry stuff I put on top kept it from having many sprouts or what, but it might be worth a try. Also pulling the sprouts off left nothing for leaves to grow on so it had to start over. Maybe that will work for you. Probably a lot depends on the age and variety of tree.

Not sure why this was bumped...but indeed, I've been surprised by how quickly potassium nitrate (typical 'stump out') or ammonium nitrate (still available online in small quantities) will accelerate the decay of large pieces of wood. I had some huge 3' X 10' logs from a tree that fell about 3 years before, that I had pushed back into a wooded area with my FEL. They just weren't breaking down very fast. I didn't even drill into them, I just carefully sprinkled prills of KNO3 into the nooks and crannies where the bark was splitting. (edit: I now remember I did put just a few drill holes in places there were only big flat surfaces...but not many.) A year later those nooks and crannies took on a porous, cardboard like appearance, with big chunks of the wood sloughing off. Mushrooms are also growing all over them. If I do another round this year, I think they will be on schedule to have totally vanished by 2-3 years time.