The Wizards have a top 5ish defense and a starting lineup (Wall-Beal-Webster-Nene-Okafor) that is ranked among the best in the NBA.
This demonstrates a clear need to upgrade the bench, add offense, and add youth (with Ariza and Okafor on one year deals) unless some currently unknown blockbuster trade involving one or more of Ariza, Nene, and Okafor materializes.
I envision this need being fulfilled through an offensive wing and a long defensive center.
Draft Express (mock draft w/o team needs taken into consideration) currently has the Wizards drafting Shabazz Muhammad at #9.
With Shabazz the Wizards would get a young wing with an NBA ready offensive game (at the ripe old age of 20). Shabazz could find some minutes behind Webster/Ariza as well as Beal. Shabazz can't play the 2 you say? I say he can guard 2s, he can create his own shot, and he can shoot. He can play the 2, especially as a backup at 10-15 minutes per night behind Beal while playing with Wall. Once Ariza leaves, Shabazz will find more minutes behind Webster (and I'm assuming we resign Webster). Shabazz would become our instant offense off the bench, backup to the 2/3 spot, and potential candidate to start at the 3 (although I agree with concerns about his size).
I don't think we should look to add a combo guard to back up both Wall and Beal. While I appreciate how neat and clean it would be for Jarrett Jack to be a combo back up guard the reality is he is not coming here and ideally there will not be more than 10 minutes behind Wall next year anyway. A.J. Price (or a better standard PG) is fine. We should be more concerned about Beal's backup.
To fill the need for a defensive center I propose we trade back into the first round (no suggestions as to how or who, feel free to make them) to target Jeff Withey, currently projected at 21 to Utah. At 23 and with four years under his belt at a major college program he also NBA ready and would replace Collins next year and possibly Okafor at the end of his deal.
Alternatively, you can look at the draft and just reverse the options to, for example, Alex Len and Allen Crabbe (just examples). But I think there are young C's to be had at the bottom of the draft and I think Shabazz fits this team well and is ready to contribute.