The Mossie could never have replaced the "heavies" simply because of the bomb carrying capacity. At least not British bombers. But with the huge loss rate of B-17s during daylight raids it has always amazed me just why the US didnt use this aircraft. The Canadians used it to great effect. And considering it could almost carry the same bomb load as a B-17. I think it was a terrible and huge loss/ of men and machines which was totally unnecessary. Im sure a lot of people will argue otherwise and im not singling out the B-17 as being a bad aircraft. Im simply stating the fact the Mossie had the least loss rate of any bomber during ww2 and was indeed a real multi purpose incredibly well conceived/designed aircraft. Infact i think it was nothing sort of genius on DeHavilland's part just as much as the Spitfire was for Mitchell. But hey this is just my opinion.
The Mossie could not have done Hamburg or Dresden.
Nor could it do the jobs using the Tallboy, Grand Slam, or the ones using the 8,000lb HC or 12,000lb HC bombs.
But they certainly could hit oil facilities (as they did historically) and factories.
Several different bomb load-outs were proposed or trialled in Mosquito aircraft, but never used.
Such as 1 x 1,000lb GP + 2 x 500lb GP/MC, 2 x 1,000lb GP/MC/TI (10 MC and 2 GP bombs were used in such an installation, but many TIs were used in this configuration, as well as a single 1,000lb TI), 6 x 250lb TI (proposed, also proposed to carry 6 x 500lb MC - the basis for the Avro carrier stories?), 8 x 250lb* TI (actually fitted to a B.XVI as a trial installation, but not used) and a 2 x 2,000lb adaptor (for 2,000lb AP bombs, for anti-shipping duties).
The B.XVI could carry 5,000lb bombs on short range missions, consisting of 1 x 4,000lb HC/MC and 2 x 500lb MC (on the wings). Or a load of 6 x 500lb MC could be carried - 4 internally and 2 on the wings - for a total of 3,000lb.
They could also carry a couple of different Small Bomb Containers, which could be filled with a few different types of cluster or incendiary bombs.
*The RAF, of course, immediately asked if 8 x 500lb MC bombs could be carried. de Havilland said that the load would put the aircraft outside its CoG limits and would be over its overload weight. The RAF then asked about 4 x 500lb + 4 x 250lb, which de Havilland took under consideration, but I have not seen a reply to that.