Absolutely, 100% agree. I'm sure Theymos is well aware of the
real problems with sig campaigns, and they have nothing to do with signature updates or tracking exactly how long a member has worn a signature. Sure, his suggestions might help campaign managers, but that's not really a problem that needs solving IMO.
Nice to hear Theymos at least considering ending signature advertising altogether. I'm not all for that, because I think they're useful to a lot of people (and businesses), but I would bet a large amount of money that the quality of posts would increase exponentially if members couldn't earn money by renting out their signature, avatar, and PM space. Bitcointalk might not become a ghost town, but it sure as hell would look a lot different than it does today.
only allow signature campaigns that pay in Bitcoin.
I also agree with this. In addition to the reasons you've given, I think it would cut down on the number of awful ICO bounties, which are usually the culprits behind all the garbage posts in the Bitcoin/Altcoin Discussion sections. It might also cut down on some of the scammier ICOs if they actually have to pay in a real cryptocurrency instead of some token destined for the 1-satoshi crypto graveyard.