To me the issue with the 3-3-5 isn't whether it's base, or people dropping down, or nickel, or any of that. It's that we have ONE guy over 280 on the field at a time, against 5 O-linemen averaging 300lbs. A 3 (or 4) man D-line going 245-285-245 with a 225lb LB thrown in there...
IMHO we'd be better served with 2 big DT's, two 250-265lb DE's, and 3 LB's. Would be much harder to "move" them back than what we currently witness (which is the D-line getting manhandled unless you happen to have a once-in-a-generation player like Alex Gubner in there).