Serverless-Only Projects for CMS

Since the surprise announcement of sunsetting serverless functions in the design manager, I am trying to figure out a way to have a faster development loop than to have to build and deploy said build every time a change is made.

This can take conservatively 20-30 seconds, for only a couple of endpoints.

As there are no UI Extensions, using hs project dev is not an option:
"ERROR Failed to setup local dev server: No extensions to run"

Am I missing something in the documentation? Or is this just life from now on(!).

Does anyone else find this incredibly painful, is there a way forward?