I like the idea of allowing characters to bank skill points toward a specific goal skill (presumeably one that can't currently be legally added to their skill columns). This has the advantage of allowing players to 'save up' for a skill that would otherwise require many painful swaps to eventually add to their skill columns while at the same time avoiding situations in which, say, a level 5 skill appears as needed from the blue. Basically, all skill points are 'spent' at any point in time, but some skill points aren't 'available for use' because there isn't currently a legal place for them in the skill column.
For an example of how this might work in action, see my post
here.