two scenarios:
blogging: To include code and images in a post, I want to type in inclusion syntax, save, click the 'add new card' link and [past in code, upload image, etc] save and continue. Currently there is an extra cycle: add new card, save, edit again, change cardtype, enter content, save. (and currently the display is messed up if you do that, doesn't return to content, i believe this is ticketed)
templating: creating *tform templates, I've want to be able to specify cardtypes in the template as I go along, rather than do a separate *rform process for each data item. (see also ease_form_building)
editor approach
just adding the cardtype dropdown on new transclusions would fix the blogging case. if you wanted this same style solution to work for templating, ideally it would recognize when you are attempting to add a relative transclusion to a *tform and take you to the appropriate *rform automagically.
syntax approach
this would let you specify the type in syntax as you go a long. not sure how it would look. maybe {{TYPE:NAME|OPTS}} then there's the problem of cards with ':' in the name. Presumably the type would be taken out of the syntax on save, but not necessarily.
The same kindof context detection would be required to apply the type to appropriate *rforms in the template scenario as to edit the *rforms above.
Crazy idea: If you went all out here allowed specifying content in the syntax, then you would have the ability to refactor a card into subcards by adding brackets around the content you want to factor out.