Say that Grouchy wasn't as cautious as he was in real life. Say that he did "hound" Blucher. Now let's say that Blucher still arrived at Waterloo, but Grouchy came up behind him (effectively making a Prussian sandwich on two pieces of French bread). Since Wellington's entire plan was counting on Blucher arriving and old Bonnie getting no support, do you think that Napoleon could have been victorious? What about in the long run, do you think that Napoleon would make peace or seek to quell the allies once and for all? What if Blucher and Wellington were captured, or even worse killed? I personally feel that Napoleon would gain massive support throughout his empire. Furthermore, I think that this new sense of national unity would swell the numbers of the Grand Armee. A naval invasion of Britain would still be out of the question, unless Napoleon could throw together a fleet of heavy ships of the line. I believe that the Britons would be quick to make peace and maybe the Austrians. But I think that the Prussians and Russians would continue the coalition.