I assume you have been to the class building site, www.ec12.info
. There, if you will look through the structure deck and the classic rig you will find this to be the least expensive process, meaning it is less expensive to buying a molded deck.
You have radio gear already so you are well along. You can advertise for radio board equipment. While you have all out of the boat you should build the system board with the sheetline attached as shown on the building site. For the EC12 the drum RMG winch is the way to go and having a removeable sheetline system is the best approach that we have now for function and service.
When you removed the ballast was there any separation to the keel seam of the hull? I ask because it looks like you worked this area. The inside looks fine and this should be a good refit as you have started from the bare hull. The is excellent.
Part of the enjoyment of the EC12 is the building and crafting. It is the hobby part of the recreation.