I believe I pretty much hinted what would be in Mys v1.4.0 before, you may find them in this blog post:
http://www.mysidiaadoptables.com/forum/blog.php?b=66
There is a good chance that Mys v1.4.0 will incorporate Multi-Currency system, or at least you can get an plugin for that. For your 'Create your own adoptables' feature, Id say it has to come down to how much the demand is. Most people want features like Stats system, thats why it will be the major addition for Mys v1.4.0. A Stats system is also one of the prerequisites for battle system(the others are attacks/ moves system, elements system and status ailment system, which will be added throughout the course of Mys v1.4.x's development).