My suggestion for a quick and easy money maker is to pinpoint a war or era that is lacking figures but has popular appeal and requires fairly large amount of troops. So that narrows it down to the English Civil War.
Are you sure that the ECW has a lot of appeal (outside of the UK) and is a quick and easy money maker? I think back to when ACTA released its ECW range and Revell released its 30YW range. I only bought one of each ACTA set but bought a large number of the Revell range. The reason that I have almost 30 of the Revell sets is that most were on sale for $1.99 or $2.99 a box. These sale prices and the duration of the sales are an indication that the era may not be as popular and marketable as one may think. I know that Revell has reissued the 30YW sets in limited quantities over the years. Since they already had the molds, this didn't cost them a lot for limited sales compared to starting from scratch.
Bottom line - I don't think that an ECW line would be as easy a moneymaker as you seem to think.
Right now, HaT has a long list of sets that the masters are already made so they will be giving priority to those. When things settle out, I think that your idea for an ECW crowd-funder is an excellent idea. It will tell us how many people will want to participate in an ECW project.