Oh! Oh! Well I am still theoretically working on that AU where Vimes and Sybil don't get married until after the Fifth Elephant because it takes that long & the time pressure of a pregnancy for Sybil to corral Vimes into agreeing to Vetinari and Margolotta for their Evening marriage, BUT as a result I have given this a little bit of thought??

It really depends on why Vimes and Sybil aren't married though. Like in mine, they may not be married but they are blatantly living in sin in front of the Emmas and everybody, and Sybil has made it very clear to the People Who Matter that she is going to marry Vimes someday, so there's not a huge change. If she's still throwing her political and social clout behind Vimes without marrying him you don't have to change nearly as much as if she just didn't exist at all.

Men at Arms there isn't a huge change, you just have to give Vimes a different thematic personal crisis other than wedding jitters, and it's not like there's a shortage of options?

I think Feet of Clay would have to change a bit more because part of what motivated Dragon King of Arms to act was the idea of Vimes (any Vimes) moving back into a place of power in the city's aristocracy, having never entirely gotten over Old Stoneface. But if you make Carrot and Angua a bit more of a threat to Dragon, I think you can rebalance things enough. And if Vimes is still Sir Samuel at this point - which he probably is? - then you could probably still have him doing the heraldry stuff, just differently motivated.

I have not read Jingo yet because I am saving it as my One Good Discworld Book Still To Read. Or until I catch up to that point in t he AU and have it as my reward. :D But I wouldn't assume Vimes doesn't get duked? I feel like one consequence of him not marrying Sybil is that Vetinari has to be a little bit more hands-on with the Vimes project, he can't delegate or shift blame to Sybil, but I think he would still find a reason to do it. But a Duke of Ankh who doesn't have the Ramkin name and money behind him is a very differently positioned Duke of Ankh.

Fifth Elephant: This one Is going to be very different anyway though, without Sybil's connection to Seraphine - this is probably the book since Guards where she has the most direct plot action, even if a lot of it's via letter-writing.

Night Watch - yeah, the only changes needed here are the result of however Vimes is different. And less time pressure on him to get home.

But anything post=Night Watch is very different due to lack of Young Sam.