See, that makes sense to me: if a game doesn't have ANYTHING resembling what you need, DIY is the way to go. It's just that with my broad base of exposure to other systems, I may be more likely to know of another game to use instead of reinventing.
I had a post-apocalyptic campaign I was designing that- in my mind- had little remaining of the known spells pre-disaster. Mages of the era were rediscovering the rules of arcane esoterica, and coming up with new stuff along the way. Meanwhile, the clergy were in the process of finding the proper prayers involved in gaining access to the full slate of divine spells.
That campaign never launched.
On the one hand, my current group is very D&Dcentric. Despite my owning most of them, we have not tried any of the various 3.X clones at the table. And the only system for designing spells from scratch in WotC's books is the Epic Handbook's spell seeds. Looking to True20 or M&M's W&W splatbook offered hope...but porting over either system would have been a massive undertaking. HERO was- and remains- out of the question, and even M&M got a black eye when I ran a Supers 1914 game using it.
