The ability score improvement/feats are baked into class logic, and your animal/minion generally doesn't get a class. The mechanism classes use is the cAttrArray which I suspect doesn't exist for a race (haven't tried it out).
The only way I could think of doing this indirectly would be to maybe to create and bootstrap abilities on your Beastmaster at 4th, 8th, 12th, 16th and 19th that prompt you for which score/scores you want to modify by +1 or +2. You then would have scripts that see what you select and then you use minion/master logic to assign attribute bonuses and such.
Things like:
minion.childfound[aSTR].field[aStartMod].value += 2
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