A much better alternative to the "single language and IDE" would be to have a single IDE but have the ability to add as many per-platform (B4A, B4i, B4J, B4R) projects as you want to a "solution".
For example:
My Great App Solution
-> Android Project
-> iOS Project (Bold = Active Project)
-> JavaFX Project
-> Server Project
The solution explorer should have a right click menu with items like "Add Project", "Rename Project", Delete Project", "Run Project", etc.
The "play" button should run the currently active project.
Any thoughts on this concept?