For what you've described, with space limitations you have, rather than a dedicated bench, you might consider an assembly table with some clamping capabilities.
Aside from chiselling what would you need a thick top for?
You might take a look at an MFT type set up. The various dogs, T tracks etc gives a lot of accurate setup capability for assembly, routing and sawing. Variety of clamping methods including a face vise. IMO its a great way to go also lots of storage capacity important for a small shop. I recently came across one on YT by Paoson Woodworking that has some very ingenious features.