I would go pick heavy rather than young player heavy in a trade for Beal.
Jrue Holiday with 1 year left on his deal was traded along with a second round pick to the Bucks for 3 first round picks, 2 pick swaps, George Hill, and Eric Bledsoe in a 4 team trade.
Holiday is not Beal but is pretty darn good player in his own right, and many would have done a Walker for Holiday 1 for 1 trade in the past. Also we wouldn’t be throwing in a negative asset like Bledsoe, and either trading for Beal at the trade deadline or a sign and trade next offseason the value should be less than trading for him now (Holiday was traded with 1 year left in his contract in his deal).
With using that trade as my perimeter for a Beal trade I would use any combination of Horford, Richardson, and Schroder maybe 1 of Langford, Edwards, G Williams, 3 first round picks, and 2 pick swaps in a trade deadline deal. You could also redirect any of those players to another team in a multi team deal as I would think any team in a playoff hunt would be happy to have for a playoff run.
I think that’s more than enough, and losing all those future picks wouldn’t bother me as I would expect us to be a playoff team for the foreseeable future. If that doesn’t work revisit again in the offseason, but Washington would have their backs up against a wall if Beal wants to leave.