I asked this over in the Astak forum but its equally relevant here and Leo is the one person who I'm sure actually knows some answers:
It appears to be possible to write programs directly for the Hanlin v3 and v5 (which are the same as the EZ Reader and Pocket Pro). (See https://www.mobileread.com/forums/showthread.php?t=59191
for one such program.)
There are a bunch of obvious utilities it would be useful to have on the EZ Reader and the Pocket Pro. For example, a program that lets you select a file on the device or SD card and delete or rename it, or a program that lets you convert from one format to another. (While I'm wishing how about a port of the Calibre conversion tools!!)
I don't really know how realistic this is, or even in what language this stuff is written in. Do the v3 and v5 have a version of Python, for example?
Does anyone have any useful knowledge on how to do all this that they are willing to share?