It is because of such cool 
contests that we should have a building limit that does not limit players from building large structures.
There should be some limitation, but it should allow even the boldest of structures to be built. A simple building element limit (similar to the current companions limit) would be a shot 
to the knee 
.
Also take a look 
at the previous competitions. Would they even take place if there was a hard limit?
Even a competition for tiny houses. In order to build anything, the owner would have to demolish part of his base to participate in the competition. Or he would have to start the game on a new server (from scratch). Because some people just want to build on official servers so that other players can see 
the competition entries.