This came sooner than I anticipated, will keep this short.
Recently used 3rd-party-program to cheat and I am currently past 500k.
Won't say how and what since it isn't relevant for the solution.
What I suggest is that the game uploads the savegame as it uploads the time for the ladder. This allows devs to check if the build can sustain the bonus round-time. To lessen the workload you can limit the control to only top 10 and since there isn't that much movement on the ladder the workload should be minimal.
Just a suggestion.
Is that really within the scope of the game? If someone wants to be a knob and cheat, they'll cheat. Wasting time and effort trying to keep up with them takes resources that could be used improving the game.