As with all such questions: ask at a consulate or embassy!
That aside, ESTA is a tourist visa program, not a work permit. Therefore I'd expect it to not be valid for business travel (which yours would be). While they may not mind someone using it to attend a tradeshow for a few days, or a conference, as an agent for a foreign company, your plans are quite different. You're going to be putting a US resident out of a job (or preventing one from getting a job), which is the very reason foreigners need work permits as companies have to show they can't get local people qualified before a foreigner is allowed in to perform the work (or that's the theory at least behind such things).
But as said, ask at an embassy or consulate.