I think using such a board for Bitlash is a great idea and would be very practical. One issue that would need to be addressed is the question of what to use in place of the AVR EEPROM for macro storage. Perhaps an SPI eeprom...
Bitlash is written to be very portable, and the source is open so anyone who pleases can take on a project like this. Bringing up the core on a new chip or platform is usually only a couple days' work, mainly involving thinking through differences like EEPROM, pin mapping, pin configuration models, etc. In this case, since the proposed platform has more generous resources, there would be less struggle with code size.
If someone is sufficiently motivated to take on such a port I am happy to provide support, both moral and technical. For an expert in the platform it would be a short slide of compiler bashing.
-br