I think that with the community these days being less and less focused on a single engine it would be a mistake to narrow down the entries to just one. I can understand the desire to keep some consistency so as to level the playing field and make it fair to compare and judge the entries, but I don't really think in the last contest we were hindered by the multiple engines used, and I don't think we will be here. The higher the turnout the better surely, and opening up to multiple engines can only help on this front.
How about we just make a rule that states engine choice has to be cleared with KFS prior to the contest kicking off, and we can then come to a consensus on what the comparable limitation on scale should be for that engine. We then lock down the engines available and list them in the rules along with the size restriction, so anyone entering after the start date has to choose from the list.