Or we could just keep Rebuild's effect but adding a weak on-gain and / or on-trash effect.
We know that cursers and Looters hurts a little bit Rebuild but not too much. So, what about : "when you gain this, gain a ruin", or to make rebuild weaker against Saboteur / Knights : "when you trash this, gain a curse".
It would still make the Rebuild strategy very powerful, but less often at least.
Because as I said, I would not like changing the whole card. I want to have a rebuild that is exactly the same, just less often dominant.