This was done long time ago already. Just use science on the holotape and the text editor will appear. I've seen only couple of people actually used this feature and it could be really funny to read something like that.
Concerning billboards, I doubt that it will be ever available to the players, as it would be vandalized by every next person (just like it happened to wiki, when it was available to edit by anyone) and thus it's pretty much senseless. On the other hand, we already have billboards in almost every town, which contain some basic info about quests available in the town and such, but they are available to edit by dev team only.