Sure, this first window is the key. Even sending one ship this year should be possible as long as there is refueling. Re-use is a benefit but could still launch without it by expending a few rockets.

I'm hoping Elon will listen to himself and not some of the more cautious voices and send at lease one ship to see how the landing attempts go. Would be a shame to build more ships for two years, in large numbers, to find they can't land on Mars.

It could be possible to fold 1 & 2 into 2 by sending a larger number of ships, but that assumes there is no fundamental flaw in the design.