I'm looking at synergizing powers with the Icewraught Sentinel's slide on primal cold. While adding the cold keyword to powers is trivial, is there any way to change a power's power-source to primal?
By the rules? No. So far, there haven't been many ways to consider something that you do being from another power source. Using the game systems flavor, a power source is how you do what you do. It's irrelevant what happens with the power, as I've seen martial and arcane powers both do the same thing, effectively. What you're trying to do is have a power (let's say a spell) come from a primal source. That's not really possible. At the point that a spell (incantation) begins to summon up primal forces, it ceases being a spell, by definition, and becomes primal. The ability would have to start out being primal.
The short answer is no, there are no feats or powers that let you turn something from one power source into another. At least, not that I've seen.
But, the rule we always use is "Does it make sense to the DM?" The answer is, maybe. You could take my above example and turn it to your point of view by saying "Well, yes, while this power is using arcane forces, what it actually summons up is something primal from nature." That's plausible and usable in home-game terms.
Just an opinion but it has nothing to do with replace and everything to do with add.
There are fire and cold powers, why not arcane and primal. I see no distinction except for an arbitrary ruling. It is literally up the GM.
I do wish rulesmakers would stop making what I call affectionately half-assed rules.
If you can twist something one way go ahead and make it possible every way so no route to a flavorful twist is left untried. This oversight from a rulemaking source that councils GMs then to "just say yes". Don't leave the lemmings without a complete guidebook to the cliff! They will miss the left turn at Albuquerque.
Some GMs are so unimaginative that they cant ever create a single thing on their own. They cant take feats on the left and create feats on the right. How hard is it really? How much of a stretch!
Martial Readiness -> Arcane Readiness Arcane Admixture -> Primal Admixture Staff Expertise -> Flyswatter of reaching spell-casting goodness
It's a hard thing indeed to run a campaign that is open and dangerous and imaginative, yet still follows a rules framework, and then play someone else's world who cant see beyond what some arbitrary authority set forth as rules in books they sell you.
Primal Infusion - adds keyword primal to any 1 power.