There have been cases where perma banned players have come back on alts and become very valueable players on the community

Unless you tell us what the books have, I don't think they mean much, but I understand why you didn't :P

Different staff members have different ways of handling different stuff, as well as logic, some might think "How would we know you are using auto-click?, you can just have your mouse stuck, or be clicking yourself, so yeah" , others might think that watching somebody do the same thing for 5 hours means it is definetly auto-click so no, these are both good opinions, but it is hard to determine which one should be prioritized so the simple, "Is auto-click banneable?" isn't as simple to answer as you might think.
At least that is what I believe could cause some contradictions or disagreements.

No that it matters much, you can just make your trap so that it can only handle x number of mobs because of crowding.
And, from personal experience, you can go a little over the limit as long as it isn't for so long and nothing will happen, but I also believe you can't get banned for it, you will just be kicked so that the admins can kill all the mobs.

@Argail Uh..changing spawners is allowed. It just won't work 100% of the time.

I don't know if it is partially allowed or it the rule changed, but the post I linked says that it isn't.
Besides, the spawners caused a lot of problems on the last server, I don't think it is something staff want to repeat again

No, in the 1.10 reset it was decided that, for economies sake, it was no longer possible to change spawners.
It was originally possible by asking admins for it (if you had an egg), but there where things made like shulker farms that kinda broke the economy and this farms were one of the several causes to make a reset.
I recommend reading this post

Don't really see how this is better than just saying "Hey, I'm selling this items for this prices, post offers here and I'll get to them when they are ready" They only thing you could do is maybe having it open 24/7, but that can be done with the help of some friends.
Honestly, although interesting, there is not much point to it

@The3xpertGamer Can there be an area where you can kill nitwits in spawn?

@DoppyRex Also I just found out how to build an op wither skeleton farm

This has been tried, results are still bad, you could try though

So all this for requesting a nitwit killing area? Which you can acheive just by throwing them on lava?
Cool story tho