I think you have a very good suggestion Scraptheold, and +1 from me. However given that most of the skill tree`improvements' are working in the opposite direction i.e. making nice working slots shorter and often less convenient for regular log on players, rather than continuous players. I have to think that it is a strategic decision of BB to do this, and therefore not likely to be implemented.
There are a lot of players that have moaned that BB devs must not play the game with what they sometimes force upon us, I think that they play too much within a work context with too many freebies at there disposal. ( If you ever need proof of this just look at the prebuilt test island and ask yourself why would anyone who knows the need for efficient production on which the game is based, place decorations ( that can not be moved) in such key production area's. And that is one of many anomalies that can be seen there). If they have access to the more `expensive/gem based' ( Lucky charm/flying settler/ exotic baskets) buffs which already cover longer periods, for free in their `development games' they obviously don't understand why we could possibly need something that is more cost balanced, sustainable and time convenient, with our own island production/playing.
A nicely thought out suggestion anyway, good luck with it.