Great work Toreth, you put a lot of thought into this and it shows. I feel like this is a great idea to help encourage activity which is always a plus. It would make all epics relatively useful in other ways besides stam gain. I can think of applications to Arena, GvG, Relics battles, PvP and basically all the parts of what make FS what it is.
It would also probably drive the price up since demand would be higher. Which in turn would make titan (or whatever else you do to get epics) hunting worth something again so hopefully the stam used would be outweighed by the FSP gained. I also think some consistency in a stat formula would be amazing. That way you could kind of predict what pieces of gear you'd need to make stronger sets.
Usually it's hard to affect positive change for all players, but something like this could only help FS. In order for this to work though I imagine that all the formulas for existing gear would need to be changed to the updated version. I don't think it would be as effective if it was just everything moving forward.
I fully support this and look forward to a positive response from the devs. Thanks for listening.