The Bourbns were the only viable option. Non one liked it but all the others had violent objectors.That's true. But the problem is....who should be sit on the throne of France afterward ? Napoleon ? He's too ambitive and dangerous ; Bourbon ? Return to absolute monarchy is as dangerous as the previous choice since the country might be plunged into chaos again with huge discontent and revolution ; Bernadotte (that Swedish crown prince who also wanted to be the King of France) ? Tsar Alexander I liked this idea, but Austria and Britain said : NO !
Then just let France return to the republic....of course it was absolutely impossible ! Not a choice at all...
Then how about letting Napoleon degraded to the position of "regency" while letting his half-Habsburg son Napoleon II directly ascended the throne ? Tsar Alexander I liked this idea, too....but Talleyrand persuaded him, this was really not a good choice at all !
Also, even the Duke of Orleans Louis-Philippe was considered an option....
How many choices I have aforementioned in total ? Just count it....six choices (in reality, five) ! You should realize that the Allied army didn't pre-ordained the Bourbons from the beginning, especially Louis XVIII was infamous for his rude and disgraceful behaviour, which greatly "unimpressed" Alexander I.
So the choice was always open ; so complex, so many....intermingled with the rivalty of conflicting interests between coalition powers. History is not so streamlined and obvious as you imagined.
BUt how coul dnay of this effect teh cmapaign enbough to give Napooen a chance? That it did not is an historical fact.