Woof Dean:
What you suggest is a perfectly valid way to go.
Our reasons for doing it as we do are:
1) We seek to come closer to the time pressures of street situations i.e. with limited time one has to explode faster and harder to finalize. In our opinion, to have no time limit tends to shift things towards time consuming tactics and strategy and a premium on conditioning.
2) To go until someone loses, shifts the meaning of the experience towards young male hierarchical competition and away from our tribal values of preparing each other to stand together to defend our land, women and children.
Please allow me to flesh this out. In our experience, there are many moments in a fight when lasting damage can be imposed. If for example a fighter with superior stick skills is in a position to badly drop someone with superior grappling skills as the latter attempts to close, rules such as you propose would, in our opinion, provoke ego driven temptations to be sure to "win" the fight now and avoid being "defeated" later. Most of us have had more than one moment where we could have permanently dimished someone else's IQ or lastingly damaged his body. My concern for the approach you suggest is that you make it hard to operate within the code of "No judges, no referees, no trophies, be friends at the end of the day".
3) Our approach also allows each fighter to experience several fights against various opponents and weapons. This allows for more experimentation and more growth.
Off the top of my head, these are the points which occur to me.
The Adventure continues,
Crafty Dog