Is there a specific need for the DMR hotspot? If you're using ASL already, you could use DVSwitch Mobile direct to ASL and not have to worry about converting to DMR.
Remote Base <-> ASL <-> DVSwitch Mobile
If you still wanted to go to DMR, you could do this:
Remote <-> ASL <-> Analog_Bridge <-> MMDVM_Bridge <-> hblink3 <-> Hotspot
You still need to have some sort of master server for the hotspot to log into, hence the hblink3. You can run hblink3 on the same host as Analog_Bridge and MMDVM_Bridge. You could even use hblink3 locally on a PiStar hotspot, but that's some advanced configuration that would need more research for me to understand it.
Oh, and I forgot to answer your other question. Also, do I need to register for an ASL node if I'm not planning on connecting to their network?
No, and I believe the ASL image startup script allows you to set up a private node, though I haven't done this myself.