I would have thought that had Blamire continued in the series then the chances are there would have been no Foggy. I agree though, it would have been interesting to see Blamire and Foggy together to see how they might have got on. I think the chances are that Foggy would have shown some deference to Blamire, who saw himself as being more from the managerial class who would occasionally put on airs and graces and a sense of superiority, especially around Compo.
As others have suggested, some of the third series was written for Blamire that became Foggy stories. It's also interesting that Blamire emphasized his military background on occasion, although Compo did point out that he only worked in the military stores. This is similar to the Corporal Signwriter putdown that was used against Foggy to bring him down to earth.
Had Blamire stayed in I think in time the early grittiness would have gone in much the same way it did with Foggy as the third man.