I could see a shake out like this...
LT - 1st Round Draft Pick
LG - Gandy/Anderson
C - Preston
RG - Villarial
RT - MW
Villarial & MW worked well last year together, and I think they will this year again. They just need to stay healthy.
As for DT, I agree, one of our biggest needs. Either a FA (although if we tag or re-sign NC, we won't have much $$ left over), or a 2nd Rd Draft Pick.
I think spending some picks on D (except the 1st rder) will pay major dividends in the years to come. We need a DT, CB, S, and LB. I think Posey will be gone with Haggan or Crowell stepping in. Behind NC & McGee we are a bit thin at CB with Thomas out. S is self explanatory. We may have top wait a year to draft Fletcher's replacement, as we have too many other needs.
Just my $.02