Imma go combo breaker here because I absolutely hate the idea of SAD design.
Stick with 4 class templates, but Instead the abilities are not tied to a specific class, but can customize that class instead. This was done to various degrees of success in 3E/PF1. Mostly it was borked though, but I hope somebody runs with it someday.
Martials:
Str - Jumping, climbing, prying, grappling, weapon use, etc...
Dex - Dodging, balancing, speed, weapon use, etc...
Con - Fortitude, endurance, physical resistance, etc...
Int - Tactics, technical application, etc...
Wis - Perception, internal will, etc...
Cha - Influence, leadership, etc...
Feats would combo the above into abilities and unlocks. Some classes would allow you to shortcut or ignore prerequisites. Like a ranger getting two weapon fighting despite not having a high enough Dex and Int or something along those lines. This way you can have a wide variety of types per class instead of being locked into the design paradigm that fighter is Str and Ranger is Dex, etc...