- Economy techs can be researched again in the next age for half cost
This one would necessitate the removal of all Imperial Age economy techs that require prerequisites. It wouldn’t apply to Market techs, since they work differently and making them repeatable might mess things up. Caravan would be an exception, though.
In case double Wheelbarrow and Hand Cart sounds broken, a hypothetical civ with this bonus would only have villagers that are 5% faster than Bohemian ones, and they’d need to be in the Imperial Age to get the full effect, so in Castle Age, they’d actually be worse in terms of speed. Carry capacity would be the real advantage.