The plugin API for Runtime Revolution has this features. You can
- declare custom commands and functions
- send messages to current card
- evaluate expressions
- get and set global variables
- get and set local variables which includes access to key/value dictionary and arrays
- get and set fields by name, index or id.
- redraw images by name, index or id.
- declare classes, modules or controls
- pass arrays or dictionaries as function parameters
- access image objects directly
So is there someone who has interest? And especially companies who want to order custom plugins?