I was thinking about the above-mentioned systems and got somewhat of an idea about it, tell me if this seems off.
Concentrated Focus (Drawback)
Prerequisites: Mental Focus Drawback.
Benefits: You have learned to push all of your energy and focus when it is needed most. You may use a free action at any time that you make a concentration check to treat that concentration check as if you rolled a 15. Doing so expends your mental focus.
Special: with GM permission, you may qualify for Psionic feats that require you to spend psionic focus, using your mental focus in place of it.
Hmm... make it 13 instead of 15. That makes it more like Martial Focus in Spheres of Might, which offers a similar expend-focus-to-get-specific-roll effect. Otherwise, it's fine. Mental focus is something you generally want to have, and even if you can get a good Concentration roll out of it, losing it is a real cost. XD That seems plenty balanced to me.
Thanks for the advi... oh it's you again!.
and admittedly I got the idea pretty much entirely because of Psionics (where you have your focus and can spend it for that concentration bit or any psionic feat that will take your focus) but as far as I know, there are no real costs to actually losing your psionic focus and no way that you can end up losing your focus in the wild without spending it (I also confess I didn't know the Saving throw bit on Martial Focus. [also no real penalties for losing your martial focus either]).
Also Whilst I'm doing this and the special "psionic feat" bit, should I just make this feat have its own feat list or go along with just having it count as psionic focus.
True, and I wasn't planning on letting people skirt it entirely, Though admittedly the only abilities I know of among the feats that would actually allow you to cheese it would be... (and feel free to tell me if I'm missing something, I didn't read every single psionic feat before this)
Psychic Mediation: reduces the time needed to concentrate to a move action: Which... okay that certainly makes it more manageable but with that same feat cost you can just remove the drawback entirely, meaning you're 2 feats to 1 if you wanted to get it just for that (granted though you gain benefits from the drawback feat still so it isn't that great)
Critical Refocus: When you spend your focus and get a critical hit with the same attack you spent your focus on. This is something that could be worryingly cheesed by crit fisher fighters with aligned attacks or psionic critical (assuming that's even a thing, which I'd personally say it's not because they both apply AFTER it's found that it is a crit) but simultaneously this is something that... when you're not going total crit fisher seems like it would be really cool. You spend your focus to make sure that maximized enhanced destructive blast connects even when someone's trying to interrupt you, crit on the blast, and regain mental focus for doing so.
Yeah, And with basically 0 overlap between psionics and spheres (well except for the Time Warden which I think scrubs out all the psionics the soulknife had), you can't really get those psionic class per day stuff without giving up being a spherecaster essentially