Such a scenario would, if I remember my Zamoyski, require Napoleon to not want to be friends with Alexander - especially because a war where the goals are "restore PLC, Ottomans get Crimea back, Sweden gets Finland back" is winnable (I think), but it requires putting aside the bigger prize of dragging Russia as a whole back into the Continental System.Neither did he even want to. He wanted to beat Russia back into his alliance system. Which is certainly a way of conducting diplomacy. Given enough incentives (mostly I think in terms of pissing him off), he might have backed hacking large parts of Russia away, recreating a Poland, turning back some Ottoman losses, but I don't think anyone had Russian conquest on their mind at the time. Too big and to Western Europeans, too alien.
Such a scenario would, if I remember my Zamoyski, require Napoleon to not want to be friends with Alexander - especially because a war where the goals are "restore PLC, Ottomans get Crimea back, Sweden gets Finland back" is winnable (I think), but it requires putting aside the bigger prize of dragging Russia as a whole back into the Continental System.
It's probably winnable, but would I reckon require putting even a modicum of effort into keeping the Ottomans onside (as OTL they stopped fighting the Russians in 1812 just after the French started). There's also Sweden to consider, though I don't really understand quite what the hell was going on in Scandinavia 1807-1814.A number of his generals were rather puzzled why he wasn't going for that and planning a two-years campaign, where the first would have looked somewhat 1807 before launching deeper into the country. It's that one that's potentially winnable, but with the need to keep in mind Spain isn't going very well for him.
Is it possible in the 1700-1900 period for anyone European to actually conquer Russia from the west even with a big POD and lead time?
Difficult to think of a contender at that point. Poles are already in decline and nobody else really has a border.
Sweden could win the Great Northern War but that just means they hold onto the baltic coast, they won't be able to absorb Muscovy. Likewise the Ottomans could do better but that's holding onto what it had not advancing further.
Austria and or Prussia could get a border if everything falls for them but they'd have to be able to not worry about the West at all to concentrate that much on the East.
It feels like a very hard sell.