I agree with you ashiaboga,
I too don't want to have to get all datacrons 5 times because I have 5 characters.
however as stated earlier in the thread it is also true that this will reduce the amount of exploring and game-play that people need to do.
though as long as you do all missions on a planet you automatically come past almost every datacron hiding place.
there are pros and cons to this idea, however I agree with the base for your idea, the implement a legacy perk/datacron upon completing a planet/all datacrons as a reward