IntelliJ IDEA / PyCharm plugin instead of PyMakr
You might have considered this already, but since circumstances change over time, I'd like to propose that merging your micropython IDE development efforts with an actively commercially developed Python IDE such as IntelliJ IDEA / PyCharm, which has an Apache-licensed Community version, might be a better use of your resources.
In this model, you would be developing only a MicroPython-specific plugin, while all the other features would come from the IDE market leader, IDEA. Writing the plugin in a modular manner would take care of majority of the issues relating to the cost of breaking the lock-in to such a product, when it becomes necessary.
There already exists a community of such plugins, and a support system for getting started.
Since I'm just an experienced user of such products, employed by a software development tool end-user company, I would urge you to set up a meeting with IntelliJ people at some conference, and have these discussions with them.