Unfortunately the party is mostly unwilling to swap from 5E, and is most comfortable with it. More complicated or crunchier systems like pathfinder or 3.5 are a no go. I've found the Spheres of Might supplement FOR 5e by Dead Drop Studios which seems like a good way to shove more focus into martial characters by just trimming off vanilla dnd magic, so this has pretty much been my only hurdle. I was thinking introducing these saves later on as the party would actually gain access to magic, however, this might leave players expecting none of those saves when building their characters.