Thanks for your comment! You are correct that the circuits wouldn't actually work because there is no current return path anywhere. Similarly, logic gates usually need separate power supplies as well. We just decided to make things simpler to keep puzzles manageable.
The ability to make your own boards is the single most requested feature, but it's also the most complicated to implement, so I can't say right now if we'll be able to add it. If the full game does well, then it's possible we will!