Stratergy 10 and 11 combination

Experts,

I was confused btw strategy 10 and 11 and after different test cases, I understood that it is more than just consideration of avail stock.

Stratergy 11 reduces PIR as soon as GR is posted for process order.

REQUIREMENT:

System should consider available stock(stratergy10) and PIR should be reduced on GR of order(like 11).

Can this be achieved by making a custom stratergy?

Am i missing something here as this requirement is not provided by SAP in stnd, any reasons for this?