Yay more Sapient golem support
Well, a lot of that is dross, the point of a golem warrior, overall, is a few things, it's to be a hard point on the battlefield (similar to a hero unit) where the enemy's attention can be drawn, and for it to be able to survive after the enemy's attention is drawn to it. One of the easier ways of doing this is to just make it huge, and if it's dumb then it kinda needs to be huge to be a threat as it wouldn't be able to respond as well as a normal combatant, however as proven by hero units, you don't have to be big to get the enemy's attention, and unlike a regular golem they can work outside just their orders, they can prioritize for themselves which is pretty good on a shifting battlefield to respond to unexpected tactics. And I believe that with intelligence the golem could become more dangerous than without, they can learn, use skill alongside what brute strength they'd have (and even without being huge I'd think Golems would be much stronger than a living thing of the same size, they are made of very heavy metal, they are the weight of the heaviest armor groups and more while maintaining more freedom of movement, and being more durable as it's made entirely of Metal rather than just armor). This is, of course, all aside from the pride of making a sapient golem, which would be quite an accomplishment I think.
You even say that yourself here, though you miss out on the idea of the Golem growing more skilled at actually fighting over time with sapience, most of our people are good because skill, this would be them but 100x more durable and 10x as strong, meaning it would be harder for anyone to lead them around as (if we fight in it) elves would be doing in the War of Vengeance, since their whole thing is being fast and skilled, with a golem as skilled as them, and about as fast it would be more likely to take them down than just fast and strong (though our golem would be strong too)
Don't think the nerfed version would allow that, since it's temporary, and would that not tie it's skill to the army it's with? As they die it would be able to do less as the people who's skills the Rune is copying die, also this still loses out on the tactics front and would the skills it copies carry over with a large golem? I mean, very different sizes, reaches, etc, could probably bring the golem to acceptable standards combat wise, though not to mastery
This would use more slots than just the one we would (presumably) use for the intelligence, and we could use those slots with the small golem for more directly strong things, like we did with meteorfall, Though that combo is a good idea for a weapon we should make at some point
I'm super biased though, I just want to make sure ya don't completely discount smart Ymir out of hand. I'm way behind now, so sorry if these were pointed out