If we're giving up that much, I'd rather sign him in free-agency.
That will be tricky to satisfy the dollar amount he wants vs Celtics able to keep vets like Horford or Schroder
I'm not worried about missing out. I'd be more worried about gutting the roster and him then deciding to play elsewhere next year. I don't think the risk warrants it.
The idea of trading for him, an expiring contract that with all probability will leave Washington next year, is that we don't have to gut the roster in the process. But if we're doing that, I'd rather take my chances in free-agency where, if signed, there'll be a guaranteed of him being around at least a few years.
I have no problem with trading for him, but we shouldn't get enamored and throw everything now for him... particularly as I'm not convinced that Beal by himself brings more to the table than what we're giving up. As it is, I'm not convinced that using cap space for him in particular will be that good of an idea (though I'd be fine if it happens).
S&T during the off season or trade within season, without gutting the roster, would be the two directions we should take. If we miss out on him, we miss out on him. We look for opportunities elsewhere.