I'm making an Alternate History on the Napoleonic Wars but I wasn't sure about the Polish-Russian boarder. So how much land would Poland get from Russia realistically? And would Lithuania be included because Napoleon did form a
Lithuanian Government during his Invasion of Russia to which it even merged with the
Polish Confederation.
Besides what already had been said by
@Jan Olbracht about plausibility of the whole enterprise [1], the problem is that Napoleon never clearly formulated political goals of this campaign even on the level of adherence to the CS. AFAIK, there is no written “political program” and even Caulaincourt, IIRC, did not report something definite.
Now, if he
really wanted to expand the Duchy, he could easily do so earlier at the Austrian expense by adding Galicia but expansion was much more modest. He could add the Royal Prussia with Gdansk but he did not.
So I’m not sure if there is a definite answer to your question based upon his known actions and upon his unknown plans.
If the idea in 1812 was to show Alexander who is the boss (by that time there was a serious diplomatic quarrel with the waves reaching many European courts) then the Duchy gets nothing because a subdued Alexander is more important than the happy Poles. If the idea is something else, then any number of guesses are possible. But, AFAIK, he was not trying to establish Polish administration in Smolensk (not sure about Vytebsk) so here you definitely have a limit. You can check if anything of the kind had been done in Vilno to get factual material for the further guesses.
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[1] With which I mostly (as “for 99%”) agree, there is always a small chance for “s—t happens” scenario (based upon which Nappy planned his campaign). Something monumentally stupid like Alexander insisting on the Drissa Plan and as a result him and the 1st Russian army are being “Sedaned” close to the border.