Thank you for your replies, guys!
I don't want to turn this topic into a CAD program discussion.
Many of the plans on guitarbuild are 2-dimensional, which means that there is no way to find out the depth of the neck socket or the depth of the pickup cavities.
Also, their Telecaster plan shows the guitar with all the hardware set in - bridge, pickguard, pickups, neck... You can't figure out the bridge pickup cavity shape or measurements since it's not shown there.
Maybe my question about the Telecaster plans should be read as:
What is the telecaster body thickness? What is the telecaster neck socket width? What is the Telecaster neck socket depth? What is the depth of the Telecaster pickup cavities? What is the total lenght of the Telecaster body? And so on, and so on up to the headstock...
OFFTOPIC:
Metric vs Imperial?
Definitely Metric. It's totally precise and you don't have to deal with stuff like 7/8, 6/9, 2/3 and so on. Plus the smaller M. units guarantee you a better accuracy. I wonder why Imperial still exists...