The success of MPS would greatly depend on templates and examples you give. Is it possible to have some common languages and concepts implemented so this can be used as a starting point for new development.
Some examples we could use:
HoTT Type Systems Examples
) like language with definable type environment
GADT, Variants and Polymorphic Variants
Higher Order Patten matching
Higher Order Kinds
Higher Order Messages
Process Algebras and Calculi
If you can impliment something like http://typesafe.com/activator
where you have both community and JetBrains controbuted templates it would be great. Also it would be good if you can give some advance examples and templates to do some of the above.