No. One of the things I was looking at was to limit the availability of siege towers in general. Make them very expensive for most factions.. and making only a select few factions capable of producing them at a less extortionate rate. For example, if you're given 300 siege points before a siege, you can allocate those points to various things.

I was also looking for ways to link this with VnVs.

I'm not a modding type, so I have no familiarity with the files. That's why I ask.