Again, yes, but it requires a person we know historically was very cautious to take a huge leap into the unknown. Whilst, as you point out, there's no accounting for age
I think perhaps you underestimate the difference between a 22-year-old just starting out and a 42-year-old with an important position to lose.
Another thought: William goes to England with the overt mission of marriage to Princess Mary; intrigue for the throne is only a tacit possibility to begin with. Then when he's there, various figures approach him... No, that doesn't work - Mary was only 10 years old, and James was against the marriage OTL. This would be William seeking a long-term betrothal that James wouldn't want to start with, much less maintain for several years.
Damn. I can't think of any clever way to get William to England.
... he has a weaker claim in this timeperiod without his marriage to Mary and added to that in 1670 the Netherlands was under direct threat from France meaning he would want to stay in place and not risk allowing the French in by taking ship to England.
Since he doesn't command in the Netherlands, would he really see his absence having that risk?
My objection here wouldn't be why would James flee, but why would he just give up. As you say, there was substantial support for James in some parts of the Kingdom and IOTL...
ITYM "ITTL".
... he hasn't overplayed his hand and cracked down after Monmouth, so no Bloody Jeffreys to limit his popularity.
ITTL James "overplays his hand" (exactly the right metaphor!); he's declared his Catholicism, his heir is Catholic, he's appointed numerous Catholic favorites to office, he's filling ecclesiastical vacancies with "tantivy men". He's responded to unrest with arbitrary arrests, and "just keeps digging" (IYKWIM).
Finally, he has William arrested and then executed. Foolish and counterproductive, of course - but James' OTL record is a list of foolish and counterproductive acts. As with Imperial Japan in 1940-1941, it's hard to argue that he wouldn't be that dumb and/or crazy.
I don't really know how I can prove this to people without page references that I don't have to hand, but Parliament really did love Karl Ludwig. They pay of his loans, invite him over to stay, and generally send him notes telling him how much they love him in the 1650s and 1660s.
"...the 1650s
and 1660s"?? The Parliaments in the 1650s were the Rump, the Barebones Parliament, and then the Rump again.
In the 1660s, there was the Convention Parliament, and then the Cavalier Parliament. It seems very odd that Karl Ludwig would be loved by both the Puritans of the Rump or Barebones, and the Royalists of the Convention and Cavalier Parliaments.
Even if he does come down with sickness it doesn't really matter imho - that is how succession works!
Sometimes. And then sometimes not. I can't cite one off the top of my head, but there were cases of "lawful heirs" passed over because they were half-witted, epileptic, or insane. Not always, but it did happen, in a few cases which IIRC involved remote foreign heirs.
Crowning Rupert risks Karl Ludwig recovering and then turning up with his own forces and claim...
Is there really any way Karl Ludwig could bring an army to England (other than a French-backed invasion)? In
theory, passing over Karl Ludwig for Rupert could be like Henry Bolingbroke displacing the Mortimer line, and open the road to a new War of the Roses. But in practice? I doubt it. I note that for all the later rhetoric of the Yorks and the fabulizing of Shakespeare, the Mortimer claim was ignored by Mortimer himself at the time.
Besides which, if Karl Ludwig
was to succeed, that would put his daughter (Louis XIV's sister-in-law!) in the line of succession. If as OTL KL's son dies without issue, then England passes to her and then to the House of Orleans... So that's a reason to pass over him. Another is his "wife", the Raugrafin, and their children, whom KL might insist be regarded as legitimate and therefore next in line. I note that OTL, the Raugravines were ignored in the 1707 Succession Act.
- hardly a recipe for peace in England especially, as you point out, if he has secured alliance with the French who may be very unhappy about an aggressive Rupert on the throne.
If France is going to push anyone for the throne, surely it would be to restore James.
I'd just also like to say more generally to people in this thread - I've never at any point actually said I think this is ASB. I've in fact been careful not to use those terms, which I think are often just rude short hand. But I do think this AHC is implausible, hence my comments. Some people are knowledgeable about the Eastern Front, some people know lots about the American Civil War - Britain 1600-1900 is my thing.
By all means share your knowledge.
However - inasmuch as the succession ultimately went to Rupert's junior nephew, I don't see that it is
intrinsically implausible.
If people want to write the timeline, write it. I'm not objecting. I'm just pointing out some of the problems.
I wouldn't try to write this; I haven't got half the background needed. I just took a stab at the AHC.
Here's an alternative. During the exile years, Charles dies, and James converts publicly to Catholicism to gain support from France. Then in 1660, the Convention Parliament then passes over James for the youngest brother Henry, who takes the throne. I think Henry would accept - he was a determined Protestant and had quarreled with James.
Henry in the meantime has met Karl Ludwig, and finds him repulsive. (He was present in Palatinate at the time of Karl's "divorce" of his first wife and bigamous second "marriage".)
Henry marries, but his two children die in the Great Plague, and his wife miscarries, leaving her fertility in doubt (and in fact removed).
He has Parliament pass an Act of Succession naming his cousin Rupert as his successor (after) of any future children. Then Henry himself dies of smallpox in 1671. But oops. William is still out there. Well, he can die off too at some earlier date. Brute force, but not impossible.
Rupert succeeds and reigns for 11 years.