If the ladders stay competitive right till the end then those folks still have to win fights to get their conquest points against increasingly harder teams as their own MMR goes up from winning. They don't just turn up and win them without effort. There's a possibility to game the MMR still by going nuts till MMR is high and teams are hard then deliberately tanking ones rating but a simple "MMR is easy to gain and hard to loose" system will make sure that it's overly painful to do.
Not sure how I quoted myself here...cba to fix it.