First off, I love this game, but what I don’t love is having to craft 1 building piece at a time from my inventory, especially when I’m working on a large build, so my first suggestion would be to add an Architect’s Bench, where you can make building pieces similar to the way the armorer bench can take over the crafting of things like twine or silk. You could possibly add a slot where you could place a blacksmith or carpenter to reduce the cost as well, but I’d be just as happy without that.
Secondly. Considering all the improved carpenters bench adds is the ability to make bark I think it’s probably more balanced somewhere around mid to late 30s. Also 10 (5 with a t4) is a lot. I was expecting a 1:1 conversion.
Afterthought: Maybe add building pieces to the improved carpenters bench and keep it at the same level. I’d still want a better bark conversion rate though.