Well, that will allow you to CONNECT them, yes, but each application will be constantly confused about which one it should be using. I suspect that the first one turned on will be the one the programs “see” and the other deck will be ignored. I suppose you’d be able to turn one off and the other on but you’d have to remember to do it in that order and you may have to close the program you’re using in order to switch without problems.
I’d get something like this:
https://www.signvideo.com/firewire-switch-ieee-1394.htm
That way you’ll never accidentally leave them both on and have trouble with the computer taking the one you didn’t mean. With a switch it would only be possible to have one available to the computer at a time. (You still might have to shut down Final Cut before making the switch…you’ll have to experiment when you get it.)