[@Crimmy]
Yes, like carpentry nails.

As for the Persona, I simply picked the most thematically appropriate one to begin with as there wasn't any indication that characters would be given access to the Velvet Room like in 1-2 or be able to advance like they did in 3-4. Levels for specific demons sort of went out the window with the later installments (Pale Rider is a level 24 summon with no special conditions in P3, for example) so I assumed it was alright to just pick whatever since this is a freeform anyway. If you like, I chould change it from Devil Survivor 2's Purple Mirror to Soul Hackers' Purple Mirror. 

The rest I'll explain over PM since you're asking me to explain some stuff I don't want to reveal right off the bat.