The thing with the Masamune though, is that from whatever means, it was corrupted and Masa and Mune were "knocked out". The person who touches the sword was therefore corrupted by an immense amount of evil energy.
This is what happens in Chrono Cross. What happened to it was never explained at all, we just know that it became an evil sword. And once beating it in battle, Masa and Mune return to their senses and accompany Serge, merging with his swallow and becoming the MasterMune.
So, there's not necessarily a reason behind the madness other than the sword corrupts anyone who touches / posses it.
Spoliers***
IN Chrono Cross, it corrupted Radius to the point where he kills Garai (sneak attack killing his best friend). Also, Dario possesses the sword at one point driving him mad, in which Karsh must attack his best friend and defeat him before he is killed. Dario regains a hint of sanity for a moment and says to kill him quick. I'm not sure if this occred in one or both dimensions, however we do know that at the end of Trigger (PSX extended ending), the MasaMune along with some man / woman was responsible for the Fall of Guardia... or at the very least a Porre uprising which allowed them control, if only for a brief period of time.
***End spoilers
So yeah, I hate to have it be the whole mad thing also, but, I'm just trying to stick to storyline. As for the fake MasaMune, I'm down for that. I don't know if it should have the same power necessarily, but it could come in very handy plot-wise...
Imagine finding the fake Masamune, thinking it to be the real one, equiping it to character whomever, him / her fighting against Alex with the real one and the sword shattering... and the real Masamune killing / defeating the character with the fake. It's a possibility to explore in at least one dimension...
Anyways, stuff should be ready for a "demo" Friday, I think I can have it done (God willing) Thursday night and let you 2 try it out and make sure it's well enough for a more public release... if you find anything wrong or want extra dialogue or something, let me know. Also gotta find a way to upload it somewhere... let me know if you know anywhere to out it.
And now, back to work.
Edit: I can really use a name for the slave... any ideas?
Edit 2: I updated the game section and put down a few screens...