Originally posted by Agelastus
Well-no. They wouldn't. The suggestion is in fact almost utter nonsense. Christian Spain had had "hegemon" states before, and they'd never bothered chnaging their name. The adoption of "Spain" was caused by specific circumstances, the union of two of the remaining three powers of the peninsula. In fact, it was a way of ensuring the unity by separating "Spanish" history from the history of the preceding states. Castile alone would have made the name change one time in a hundred, or one time in a thousand, if that.
Just call them exiles. I've never been in favour of "province basing" leaders. I have been in favour of an annexer getting a small and random proportion of an annexed nation's leaders, but that's a different issue.
So, no-they shouldn't.
I've suggested a "support Coulumbus" event for Portugal myself. The AI having a 95% chance to say no or something. That would be really historical and allow Portugal a potential advantage over its' larger neighbour.
Spain - ok we disagree on this one. The game concept of Spain is that one nation in the iberian peninsula evolves into what we recognise as spain today. If the leader files were heavily modded (see below) then the Create Spain event could be limited to a temporary dynastic alliance.
Leaders - that's also a bit of a fudge

Mind you it's one I would support but the coding is not insignificant. It won't be in first patch I guarantee and may not be in until one kind soul sits down and does most of the work. Volunteers?
Colombus - yeah but I'd prefer itt went something like
"Do you (Spain) want to sponsor Colombus
A - Yes. Cost 200 ducats. (85%)
B - No. Activate Portuguese event
Do you (Portugal) want to sponsor Columbus
A - No. Activate Genoese event
B - Yes Cost 200 ducats (chance 0.15*0.15 = 2% approx)
Do you (Genoa) want to sponsor Columbus
A- No. Give Columbus to Spain anyway (private backing 0.15*0.85*0.85 = 11% approx)
B - Yes Cost 200 ducats (0.15*0.85*0.15 = 2%)
The order is not historical I know but is weighted to give player spain a good chance (85% costs 200 ducats, 11% for free, 2% portugal, 2% genoa)