There should not be any problems with importing an updated deck, I have tried it myself several times. You can start the deck right now if you want, no reason to wait.
I'm not sure what you mean by saying my decks need a huge amount of work. The grammar deck will have 7 levels and it is quite close to being finished, maybe it will have 300-400 more cards. There will be a separate deck for levels 8 and 9 and it will not be free. But that is at least three years into the future.
The vocabulary deck, I'm still not sure what I plan for it. I'm sure that eventually I will reduce the number of words available for free, but I also want to add example sentences. And the order of the words past 2000 will have to be improved before I can sell them. Anyway, for now this deck will stay as is on the Anki website.