You can do it, you just need to have one script turned off all the time and then turn the other one off and this one on when you want to use this battle system.
I'm no Ruby scripter so I can't help you with this and it's been a real pain in the arsenal to figure out how to do it with my own to battle scripts
(You're not the first one to come up with a normal battle system and a tactical battle system for their game
)
But at least you now know that it's possible