Can you boost your initiative mid-combat?

[Fearspect]

If you had an ability that increases your initiative for a number of rounds, would activating it have an effect after initiative has been rolled?

Specifically, this would be for an Arcanist taking the School Understanding(Divination) exploit to gain the school ability to always act in the surprise round and add half your wizard level to your initiative. Unactivated, this provides a flat +1 initiative and the acting in the surprise round, but for the cost of an arcane pool point you can act as if you had more wizard levels for a number of rounds.

[RumpinRufus]

You get a bonus on initiative checks. You only make the check once per combat, and if you've already made your check then it confers no benefit.

[Bandw2]

delay until your before the guy with the highest init roll. :D