Your play is fine. NH. I think A7o from BU is strong enough to isoraise vs a random limper. But if you know he is really tight, like 16/3, then it might be too loose.
If opponent is full stacked, usually you can raise J9+ Q9+ K9+ A7+ A2s+ 67s+ 22+. All these hands can flop middle or top pair really often, and with low pocket pairs we want to build the pot so that if we hit a set, we can play for stacks.