So in designing my own homebrew world, I decided to implement a few minor house rules. This idea snowballed and lead to me incorporating a great deal of alternate rules from various Pathfinder books, as well the Spheres of Power system. Right now, the alternate rules I'm using from Pathfinder supplements are:
Armor as damage reduction (Ultimate Combat)
Wound thresholds (Pathfinder Unchained)
Automatic bonus progression (Pathfinder Unchained)
Revised action economy (Pathfinder Unchained)
Now, I'm aware that adding all of these rules, in addition to the Spheres of Power system, changes the entire game. I will need to add or change minor things about all of these rules to make them fit together with one another. However, I'm worried that even after tweaking everything, there will still be some glaring problems with the system that I'm not seeing, or that the rules themselves will not mesh together the way I'd like them to.
What I'm asking is for anyone rules-savvy to tell me how a game like this would play, and to offer advice on how to fix any potentially major problems with such a system. For instance, using wound thresholds means that healing magic becomes more important, but is a party without a dedicated healer doomed? Armor as DR means that attacks will probably hit more frequently, and the revised action economy allows up to three attacks per round right at first level - does this mean melee combat will be too deadly? Will higher CR monsters be horribly unbalanced?
Please note that this is a work in progress, and I have not yet had the time to actually playtest any of this.