I was the last of the Bledsoe apologists, and I still believed in him as late as the Romo takeover.
On "Canton Hall," I think if Drew had one or two more good seasons (think, Buffalo 2002 or New England 1997), he would have been a near-lock. After all, how do you keep a player out of the Hall who is top-10 or top-5 in every category at his position (which he would be given 1-2 more good years)? Lest the argument be made he didn't lead teams anywhere, he won two more AFC Championship Games than Dan Fouts ever did, and no one disputes his Hall status.
On Foxboro, see what someone (I think it was Felger) wrote about the way the Packers do it. They have three tiers: retire numbers (only about 4 of these), "Ring of Honor" (about 15 of these, including the retired numbers), and "Packers Hall of Fame" (about 50 of these, including the prior two). The author seems to think this is a good way to do it, and I agree with him.
Certainly Drew would deserve the third-tier, HOF consideration. Is he one of the top-15 players in team history, and deserving of a ring of honor? Absolutely. Number retired? I could see the case going either way.
If your standard for number retirement is an average of 1 every 20 years (as is the case with the Packers--a generational number retirement, in other words), you could make the case.
Among retired players, the best Pats of all time probably are (in no order):
--Drew
--Hannah
--Tippett
--Grogan
I exclude the Mike Haynes' of the world who left and are better-identified with other teams.
I think that's not a bad list to start with. From this era, you're likely only to add Brady and Seymour. In my mind, Drew deserves to be in that conversation.