Re: Order/DE
1) I think this one is a definite to happen at some point. It makes sense, fits with plot and isn't too hard to fit in.
2) Also works. I think a muggle hunting bill or half breed one might work better, and doesn't even have to be passed, just discussed at length in the papers and in school.
3) I think that fits in with the beginnings of the Order/DE - especially for the DE where older/more vocal students may try and persuade people to join Voldie when they leave school.
4) Depends on how it would be plotted (some kind of NPC perhaps) but again, with the right way for them to come into school (if an outsider at any rate) it could work. A DE recruitment thing could be held at one of the pureblood society events in the holidays - I'm thinking the memorial ball for Julius Rowle would actually work pretty wonderfully for that, with him being killed by a Muggleborn and all - probably lots of hate speech flying around there!
5) I think that's pretty likely - perhaps it would get the backs up of Voldie supporters as well!
6) I think that's probably less likely, but might perhaps work further down the line as a mooted, desperate suggestion from someone in the Ministry as more attacks etc happen?