Gargoyles that can be Animated and Controlled
Basically, I believe gems should have the opportunity to be more of a continuously useful resource. Currently, at end game gems become rather pointless despite the fact there are SO many variations of them.
I am suggesting two things here.
1. Animated Gargoyles for defense
2. Gargoyle Rune
So, to put things simply, I believe you should be able to craft statues which utilize stone and gems that animate once hostiles are near. I would imagine each castle would have a cap of 10-ish of these. The different types of gems you put into these gargoyles will give them a unique combat effect/bonus. If they die, you need to craft them again. They're dead permanently.
Next, while the siege golem is for offensive raiding, I think it'd be rad if you could create a defensive/combat oriented Gargoyle rune. This would let you summon a massive (but smaller than the golem, think like.... Fallen Angel size.) stone gargoyle that you can take control of for a certain amount of time.