I was looking at the twin souls perk and see that it changes an entry point in order for me to have more than one summon at the same time.

My question is how would I modify that same value within a script (which may be attached to a quest or the player)

Bump

Bump, last time

You can't access it directly with scripts, but you could make clones of the perk with different values and use the http://www.creationkit.com/AddPerk_-_Actor & http://www.creationkit.com/RemovePerk_-_Actor functions.