If the Swedish invasion of Russia would have happened 1700-1701, the circumstances for the Swedes wouldn't have been worse than they were in 1708-1709 at least. Charles was already gambling, when he decided to attack the Commonwealth and left his rear open for the Russians. So, why not to do it vice versa, it wouldn't have included any more risk to leave the rear open for Commonwealth and secure the supply with the garrisons of Riga and Narva and raiding the depo in St.Petersburgh constructions. For real Charles invaded Russia in winter 1708-1709 and it was a terrible winter, in 1700-1701 the winter was mild. Besides, Charles wouldn't have faced opposing forces, because the enemy was defeated and could not have practiced scorched earth -tactics.
In summer/autumn 1701 Charles would have found his allies from the Ottomans and the Cossacks of Ukraine. This alliance Sweden-the Ottomans-Cossacks of Ukraine could have defeated the remaining enemies, the Commonwealth and Denmark.
Here is the map
https://upload.wikimedia.org/wikipedia/commons/0/08/Great_Northern_War_Part1.png
his rear was open, but the Russians were beaten and the Commonwealth was besieging Riga (the second largest city he had). Had they succeed they could storm the Baltic Provinces which is a game over for Sweden. Therefore he have to move there and relieve it. Until he neutralized the Polish-Saxon army which is about Grodno and Fraustadt he was always under the threat of getting cut from his bases in Sweden.