Overall, i'm really liking the idea of having OBs or PSs not linked to WP requirements.
But, i'm not sure if having it EVE based only through a timer would be such a good idea. Remember what CCP always says : Both games interact but they need to remain independant. At least for now.
So, OB\PS mecanics should be a Dust side thing. But, that doesnt mean you can't think of various solutions :
Cooldown is actually a decent option. But tough to figure out as it would need to have a constant number of SL in game so you would now which timeframe is ok for this.
Let me explain. You can have games with only 1 squad and the rest in the general pool of unassigned players. With this scenario, you could give an OB to the SL every 5 minutes. Would end with 3/4 OBs in most games.
Now, take a game with 3 squads (6/6/4), if you keep that same timeframe, you will reach 9/12 OBs in a 15/20 minutes game for one team. It's now a bit too much and would probably require a higher delay between strikes.
Finally, Dust allows to have more squads but filled with less players. Say 5 squads of 3 players. There, you'd reach 15/20 Obs.
See where i'm getting at there ? So, having OBs based on a timer would probably require something being done on the squad mecanics. Like having a maximum set number of squads and no longer randoms being left out unassigned so both teams always have the same amount of SL and thus OB\PS. Would also allow even random dudes being SL (randomized choice) once in a while, using OB and it could be a plus for New Players.
But there could be downsides : Selected SL AFKing MCCs, SL hiding not afk but just to use their OBs and play it safe. and probably other stuff that dont comes to mind yet.
The other option is to add an in-game item that would be needed to use to get an OB. I remember (i think it was praetorian in Cast 514) hearing talks about Dust 514 beacon that players would need to carry to a specific area to pinpoint the strike.
I also like the idea of linking OB\PS to a specific action that would require team efforts instead of an addition of WPs. WOuld add another layer to the game.
I dont know, you could imagine a scrambling facility that would jam War BArge or Ships firing system. The team owning it would make it possible for its asset to fire. Then it would reset (acting as a kind of timer) before it's hackable again. Etc..
Like a secondary objective.