My plan is to design PCB for Pavapro, to have it more compact and elegant, though one can simply hook up a few modules to trinket pro.

The PCB contains even full trinket pro design (though slightly adjusted). If you are brave enough, you can solder the parts for trinket pro (including a bit tricky QFN AVR and tiny resonator). If you don't feel like this is what you want to do, just leave the middle part unpopulated and solder your trinket pro via pin headers. The rest of components are no-thrills SMD parts.

I even left some "breadboard" area on the bottom side to allow future modifications and hacking.

For my design, I recycled the original design files from adafruit. The original PCB wast designed to meet with the particular PCB manufacturer rules, but it wasn't very friendly for home manufacturing or cheaper PCB manufacturers, so I had to move a few parts or PCB tracks, so it can be manufactured with 0,15mm/0,15mm track/isolation witdh, 0,5mm drilling, 0,3mm pad size and no capped vias. I sent the design files to fellow hacker to manufacture it, I'm waiting for the result and working on the software in the meantime.

The PCB design for Pavapro, as well as modified trinket design is on my github.