That would be really
nice to have. OtOH, designing around the lack of them is part of the challenge. Every time I find myself wanting them, I just think "These are tinker toys, not an erector set." Maybe you could be allowed a limited number of pines per design? Nah... probably too complicated.
Oh! This person did manage to make a scissors type lever arm, so it's not un-possible!http://fantasticcontraption.com/?designId=633624
As a vaguely related suggestion, when I started playing I couldn't figure out the "wart" looking lumps on the wood rods. I thought they were supposed to be a connecting node to allow a mid-rod pivot. Now they're just annoying clutter. Perhaps they should just be removed? I normally stay in simple-graphics mode, but overall the rods are just displayed too wide -- I can't see enough of what's behind them when they're close together.