The past TES games with construction sets didn't really allow anyway to create new skills or any magic effects, because they were all hard-coded and generally any mod that wants to go in that direction has to make really ham-fisted attempts to work around the hard-coded restrictions.

Hopefully with the new engine, there'll be some chance these things can now be modded?

Because, someone out there would love to mod in climbing, crafting skills, weapon types, or whole different schools of magic right even if it isn't in the main game by default?

Skills were still hardcoded in Fallout 3/NV, but you could create new MGEF objects and have a far higher degree of editability as well. Granted, the system was more along the lines of just "effects" since FO has no magic, but the underlying systems are closely similar to Oblivion's.

I like both of the ideas the only problem is, like you said, these are hard coded into the game. Meaning you would probably (not totally sure) have to have been one of the people who did the original programming to even know where to begin. I suppose if the other skills are fully editable you would be able to learn quite a bit from them.

The problem is connecting the new skill improvement to a kind of repeatable action that has not been connected to any other skill. What would be the individual action, and how do we connect them to the new skill.

I was hoping at the very least with a new engine; they might have more freedom to expose more functionality (i.e. not hard-coded) than when they were using the gamebyro in Oblivion to modders.

Granted, there is tons you could do with a scripted magical effect, but that's so far apart from the given construction set. And then needing FOSE,OBSE, .. SKSE?