what actions do you allow players to make when nades are tossed their way? let them pick them up and throw back? or do they blow up after scatter determines where they bounce? would you allow a player to make an athletics test to make a soft catch and another to throw it back? or would you only allow that if they held their actions until the nade got thrown their way? any other ideas?

Non-grenadelinked or airtimed grenades blow up on the next pass of the thrower (which is odd, but usually workable.) Rules for throwing grenades back are on pg. 107 of the CC.

As long as they have actions before the pass ends, they can do anything they like.