What if he had been gotten rid of---could the level of seriousness been brought to a level between the mostly serious of TOS and the 'completely ridiculous' that it devolved into?
Could the show have had youth appeal and gotten adult or serious sci-fi fans to say...
"That was a bit of sci-fi fun." as opposed to
"what a bunch of kiddie-crap."
All you have to do is look at the other 3 Irwin Allen sf series and you can make a good guess. The plots would have become repetitive and silly with weird silver skinned aliens and lots of "duplicates" of the regular cast to save money. It never would have retained the feel of the first episodes and probably not lasted as long as it did.
So you are saying that without the Dr Smith/Will dynamic it would have failed earlier?