That would be tricky to do. A good exam question will be so ambiguous that it will turn cases inside-out or complicate those lines for you.
For example, on my first Property exam there was a question about adverse possession. (In case you haven't got there yet, adverse possession is a doctrine whereby if you have been accidentally using someone else's land as your own long enough and without hiding it, the law will just grant it to you as if it was yours all along.) Typically adverse possession requires a fence as a clear assertion that "no, I think this is mine".
I could have flipped right to the fence issue and cited that case that supported the plaintiff, but the fact was that he was running a farm that happened to be part apiary. I argued in the defendant's favour that swarms of buzzing bees are just as effective a form of exclusion as a fence --- if not more. So the case would have been put in upside-down.
The reason why maps are designed the way they are, (i.e., to flag issues rather than determine them) is because of your part in the exam room: knowing the cases and being able to apply the reasoning and facts. Your map should put you in mind of what issues are in play. It's your job to play them.
On top of that, the principles in the cases don't always cut plaintiff-defendant. Sometimes they cut owner-renter, or purchasor-seller. And then the next case might cut the next way on the same principle. And although Case X says the plaintiff wins, it might do so on Principle Y, which isn't present in the exam question --- so the plaintiff-wins case actually supports the defendant here.
Without knowing exactly what you were planning, it seems to me that line-drawing exercise could become disorganized and unduly decisive pretty quickly. But if you've got a better method, by all means, invent it! The common law generally could use your input!