The A330's cruise speed at 541 knots (mach 0.82) is only 19 knots slower than the B-52's maximum speed; the Vulcan's low level operational speed was 375 knots and high level was mach 0.86.
Heat signature is a function of podded engines that could easily be improved; The Typhoon achieves a reduced radar signature by having as few metal parts as possible, and being built to a very high tolerance to avoid any radar reflecting gaps between parts. The A350 with composite wings would be a than the A330 and it's would have a far smaller RCS than a B52. Ironing out any noisy areas with RAM would not be prohibitively expensive.
Battle damage is a function of the hostility of the environment and incredibly random. A small piece of AA shrapnel hitting the fuselage has a different effect from it hitting the engine. These two scenarios only differ by random chance.
The B-52 ain't designed to be maneuverable - I think it's the only plane that takes off with the nose pitching down!!
The military always come up with hundreds of reasons why their specifications (that cost the earth) are totally inflexible. When the pressure is suddenly on in wartime, the Military suddenly find loads of ways to work more efficiently with eberyday resources available. In the lead up to the Falklands, MV Atlantic Causeway (sister ship to Conveyor) was converted into a reserve aircraft carrier compete with 140m runway within 10 days; after a close encounter with an Argentine 707 prompted the fitting of Sidewinders to Nimrods, the first of which was complete 8 days later...
Generally military stuff is built to military, not commercial, standards for a reason. Although there definitely is a tendency to gold-plate everything in sight, most specifications are there for a reason.
Anyways, it's not efficient to start converting A330's or other commercial peoplecarriers as bombers because:
a) there already are plenty simple, cheap bombtrucks around which generally has only used up around 2/3 of it's lifespan or less; the B-52.
b) changing a commercial carrier into a bomber is going to be hideously expensive; imagine cutting a hole into a pressurehull which isn't designed for that to name just one of the problems. At most you'd be able to use the wings of an existing aircraft. The C-17 would probably be the most suitable of all transports around or so I've heard.
Ever heard of the P-8 Poseidon program? It's a relative simple conversion compared to converting to a genuine bomber (the P-8 wasn't required to have that much of a payload) and even that was extremely expensive.
c) the fly-away cost of an ordinary modern peoplecarrier is hideously expensive to start with; why would you buy a COIN-only aircraft for 250 mln USD and up? If you're going for a COIN-aircraft, it should be cheap.