So you want to in real time modify the specific strategies bonus.
The StrategyChanger function in the racial ai's is where these bonuses are added. You will have to create a variable in place though as the bonuses are just placed in the code instead of storing them in a strategy array. You would have to add modifier variables for this to work. Something like below
set rp[STRAT_NormalElf] = rp[STRAT_NormalElf] + 0 * enemy_air+ modifier_variable[STRAT_NormalElf]
Then in your event where ever you code it would be something like follows.
set modifier_variable[chosen_strategy] to "whatever"
chosen_strategy is a actual variable in AMAI that tells you what strategy AMAI is currently using. Of course if you need to set it to a certain particular strategy your have to enter it by its code name (STRAT_codeindevloper).