kam i love this question... i've thought about this on and off without ever writing anything down (knife roomba that chases z's ankles was a joke but he would. he would), but i think he'd for the most part make things that ultimately serve literally no purpose or are just practical things that aren't necessarily needed (i'm thinking of that robot that's supposed to feed you soup and just fails miserably).

he grew up recreating models of warmachina and learning about their functions thru his father's position working in the enceladeum, and that idea of a machine's purpose being dependent on its creators intent stuck w him (some robots are meant to kill). as a result i think he'd find the most joy in machines that aren't programmed to do things that are technically useful. here's my magitek bit that is actually just like a flying purse, it holds things for me. i could do this myself but it can, too. here's my robot that opens and closes the drapes when i give it a command. this is an unnecessary task for a robot to do.

i've gotten a bit out of hand answering this but i guess the short of it is, his projects would always be small, pointless, and just "for fun". if things were different i think he'd have longer term projects that have more purpose - like as a scion rather than the WoL, i imagined him joining up w cid and the ironworks w/ an ultimate goal of bringing garlean tech to eorzea (infrastructure & robotics meant to be helpful to people would be His Deal) - but as WoL he doesn't have a lot of time to begin with, and there's just some kind of escapism and pleasant comfort to be found in making something that "means" nothing