That would be cool for tourneys... So maybe make a 'Tourny-Only-Option'? This way multis cant abuse it, and it can still be used in a tourny-loving manner?
There's a work-around for that: Tournament organizers who're worried about stalemating have established a round at which the game for the game is over for tournament purposes; while the players might continue to play the game, the 'winner' of the game for tournament purposes is announced based on terrcount, troops, etc.
I see mainly negatives with the idea for normal play.
Some players enjoy being part of crazy-round games, so would dislike this option. Especially true of a few Battle Royale games.
The option is likely to encourage intentional stalling... people who won't attack, not because they risk another player massacring them, but because they're higher in troopcount so simply wait for the requisite number of rounds to announce them the winner.
One hope the site must have, since it's a business, is that people playing for free will ultimately want to buy premium. One reason people buy premium is because they want to play, and some games stall and hold up their allotted number of games. If games end at a certain round regardless, that could detract from the player's wish to purchase a premium account.