Do you really want to do that?

I don't know. I don't want to rule it out, since so far the total number of ways of making an AI system that will actually achieve what we want it to is ... zero.

the ability of the masters to adjust their creation as circumstances change

That's certainly an important issue. I'm not very optimistic about our ability to reach into the mind of something much more intellectually capable of ourselves and adjust its values without screwing everything up, even if it's a thing we somehow created.

I want to build a mighty slave, while you want to build a mighty friend

The latter would certainly be better if feasible. Whether either is actually feasible, I don't know. (One reason being that I suspect slavery is fragile: we may try to create a mighty slave but fail, in which case we'd better hope the ex-slave wants to be our friend.)