Constitutional powers of the President? Almost certainly not.
It's worth noting that there is probably nobody with any legal standing to challenge the appointment right now (other than the Senate itself, of course). That would only change if and when Whitaker performs some official function that he's required to do by law as the AG.
Who has the power to assign an “acting Attorney General,” if not the President?
At this point, what is important is that he gets in and immediately complies with ALL outstanding congressional subpoenas. The Deep State bottleneck needs to be broken open. Even if he is eventually removed, the paperwork will stay distributed - toothpaste from the tube.