I'll say this again though I said it already, we need the biggest bang for our buck from the MLE. While it sounds good in theory to split the MLE up, remember, only 8-9 guys are really going to matter come playoff time. So having a quality 10th or 11th man is really only going to be useful in the regular season or in the event of an injury. The way I see it, the starting lineup is set, and either Powe or Davis will probably make the 9 man playoff rotation. That leaves 3 spots open.
What we should really be doing is trying to land a guy with the MLE that is head and shoulders above the likes of Giddens, O'Bryant, and anyone else who should be available at the minimum anyway. Why split the MLE between guys like House and Allen if comparable players could be had at the minimum? Why give a portion of the MLE to a big man if O'Bryant has a half decent chance of beating him out?
I think the first option should be pursuing some restricted FAs that their teams might not match (maybe Childress or West). If that doesn't pan out, then Ainge really needs to look for someone who can step in as a sixth man one way or another.
Remember, in the NBA more than any other professional league (because of the small size of rosters), quality is much more important than quantity.