Hover over can happen accidentally as you are placing ghosts to plan so you must toggle the effect on and off when building. Hover over works for building large blueprint swaths but something like the blueprint shotgun or bots is fairer for that use case. This mod however; if it activated on clicking a ghost, is how I would expect the vanilla game to behave and would be perfect for filling that earliest game niche.

It is indeed a very good idea. I implemented it in version 0.3.0 as an additional mode, with the options 'on hover' 'on click' and 'disabled'.
Thank you for the suggestion.