Józef Poniatowski died at Leipzig, so with a POD before the battle there's a chance he could survive. Personally I like the idea of Józef marrying Princess Maria Augusta of Saxony, the only child of Frederick Augustus of Saxony & Warsaw and the so-called Infanta of Poland, and jointly ruling over a smaller Poland.
Matteo, I think your WAY overestimating the coalition's bargaining power. If the King and Tsar, along with their command staffs, are captured and the French win a decisive victory at Leipzig, then the Coalition will probably collapse.
If we're assuming the Coalition is routed and whats left of the armies retreat, either to Bohemia or breaks up along national lines, then Napoleon's in the position to regain the tactical advantage. Breaking down your ideas for the peace:
1. None of the three eastern powers would be in a position to dictate anything about the Confederation of the Rhine. Napoleon still controls most of Germany and I'd assume Bavaria, Saxony and the other states are still loyal. So on route there unless the Coalition recovers, beats Napoleon elsewhere and moves into Germany.
2. Tyrol and IIllyria MIGHT be returned to Austria, if the Austrians can quickly make peace, switch sides or if their army is relatively intact. If their army is crushed then Austria's out, as this was basically their last role of the dice: they were running out of manpower.
3. Poland's going to be the main sticking point. Remember, Prussia's King and Russia's Tsar are in Napoleon's custody: would either power be in a position to fight on here? OK maybe Prussia but Russia, the absolute monarchy deeply dependent on the Tsar to keep the government running? I doubt it.
3 and 4. WHY would Napoleon, who's just pulled a coup de grace, give up the Netherlands and Spain? The coalition, on the other side of Europe, would be in no position to dictate such terms, even with an ATL victory at Leipzig. Nappy would laugh in their faces.
5. Legally the Napoleonic Kingdom of Italy was still set to go to Eugène de Beauharnais, Napoleon's former step-son. While Napoleon had hinted at wanting to leave both France and Italy to the King of Rome, nothing had legally changed by 1813.
6. Finally, only Britain's in a position to give over colonies to France, which I can't see them doing at this point. Although if a permanent peace is established in Europe between Napoleon and the sixth coalition forces, then we could see London finally come to the barging table.
Britain would probably get an evacuation of Portugal (after all, Napoleon had been driven out of Portugal in 1811, so its realistic for Nappy to give on that), an end of the Continental system, recognition of British control over Malta, the independence of Sicily and Sardinia and maybe some kind of compensation over Hanover and to the House of Orange. On the flip side, Napoleon would get Britain to withdraw its army and support from Spain, no more financial support for French enemies and maybe some of the occupied French colonies returned.
While some of my ideas for a permanent Napoleonic peace might be wrong, I think they're more in touch with the situation on the ground and what Napoleon would actually accept.
I think you should not either overestimate the bargaining power of a country isolated against the coalition of most of Europe.
In october 1813, France no longer has the resources to fight for another 2 years. It is exhausted and needs peace.
And France needs to secure a real and lasting peace with Europe and especially with Britain. Not another truce waiting for the next coalition. In october 1813 Spain is lost for France. France needs to pay a high price for Britain agreeing to a lasting peace. A Dutch independant State is a very important opening on Europe and Germany for british trade. And free access to all of Europés markets (except France of course) is a part of the price Napoleon can't escape paying if he wanted real peace with Britain.
I think the global set peace settlement I devised still is very very favourable to France. Such a lastable settlement would be a real triumph of France's multi secular strategic ambitions in Europe. And it would give France the iron and coal resources it OTL lacked to turn it into (with Rhineland and Lombardia) an industrial superpower on parity with OTL Britain and wilhelmine Germany by the late 19th and early 20th century.