I chose "None" (plus RLKAG).
WR is well-stocked now.
TE will be fine when Hollister gets healthy.
RB - Assuming that Farrow is promoted this weekend, they're probably okay for a couple-three games while Sony heals. Reinforcement for the position may be available fairly soon from Burkhead coming off IR as soon as week-13 (after the next four games).
OL - The quality of depth at OT is the only potential issue, IMHO. The question is whether or not there's a significant upgrade to reserve-OT available via trade, especially given that there's limited time left in the season for a new guy to climb the learning curve.
DL - Interior DL play has been no more than adequate. They've been making tackles/stops and limiting running lanes better than last year, mostly due to Guy stepping up. OTOH, they're not getting any more pressure than the 2017 crew (except for Butler). It would be nice to get an upgrade for the pressure aspect, but I'm not sure that there's an affordable player available (e.g., Grady Jarret would be an affordable upgrade, but is highly unlikely to be available).
DL - Edge play from Flowers has been excellent. Wise has been solid all around. Clayborn has been getting good pressure, but his edge-contain, especially against mobile QBs, has obviously been poor. They have a 4th edge guy - Simon - who could improve the overall picture significantly, whenever he gets over his shoulder injury (hopefully soon).
LB - HT, KVN and Roberts have actually been playing very well. For the limited amount they've been used in coverage, they've been at least adequate. KVN has produced as many total QB pressures/hits/sacks as either of Flowers and Clayborn.
Run-D for the front-6 has been fairly adequate, except against running QBs. Watson, Bortles and Trubisky have accounted for 20% of the rushing yards the Pats have given up. Trubisky accounted for the longest run from scrimmage (by far) and one of the three total rushing TDs the Pats have given up this season. Against non-QB players, the defense has allowed an average of 88 rushing yds/game at a 4.16 ypa clip, and a total of two rushing TDs through 7 games. They've also allowed the 6th lowest % of rushing 1st-downs (25.5%).
The LB position "feels" thin, but, again, Simon plays an OLB/DE role, so his presence may help that.
DB - Aside from one big receiving TD apiece given up by Jones and JMac, CB play has been good. Extracting those two plays ... in 1172 snaps, the combo of Gilmore, JMac and JJ has allowed a 46% completion rate, a 10.5 YPC, and 3 TDs. They've gotten 21 total PD+INT versus 5 total flags against.
The biggest problem in coverage, statistically, has been DMac, although the safety unit in general has been much worse than the LB unit. If this isn't due primarily to scheme execution issues, then an additional (accomplished) safety might be worth trading for.
OTOH, JC Jackson seems very talented, though raw. And Dawson appears to be returning from IR soon. So, general DB reinforcements may already be in hand. Whether or not this will be enough to reduce the coverage problems with the safety unit is something only the coaches would know.