Hey Boromir, I totally get what you're saying. It's always frustrating when you want to merge plots, but another person's plot is in the way. Unfortunately, the only way to move someone else's plot is to have a Mod change that plot's ownership, then copy the build over, which is a bit of an inconvenience. However, there are other things you can do if you need a certain plot.
Firstly you could /plot delete your current plots and fly around until you find a fittingly vacant area, then /plot claim the ones you need. This is a safe choice if you haven't already built anything on your plot.
Of course, if you do have builds on your plot, that may be a problem. If this is the case, you can copy your build with WorldEdit (which is attainable at the /shop) and paste it to another plot. If you need help with WorldEdit I'd be more than glad to help you, and I'm sure you could ask most players to help out as well.
It may be best to ask a staff directly though, and I recommend doing so before you do anything. Feel free to message me if you need anything.
Cheers!