I quite like the idea it would kind of make the similar to a game of chess in which you have to play your pieces carefully.
I know no one has tried it out yet I'm just pointing a potential problem that could arise from it.
In case you missed it the "diabolical plan" is a joke, I'm merely pointing out the danger and the possibly seriously aggravating part of the mechanic. A limit of sorts, on how many times one can be assassinated?
If you think about it someone with this new assassination mechanic and with some help could theoretically silence their opponent for the whole campaigning period