hey it's not spam if it's legitimate, full thoughts and concerns and you're not just repeating the same ones over and over!
personally tho, i actually do use blueprints for exactly what you described (i make a blueprint of a fence post and some railings, then just copy and paste it to make the rest of the pen or whatever it is), the only problem is that blueprints don't snap, but i haven't had issues with that yet since i can get everything close enough.