I think you should be, and will be, praised for your effort, is what I think.
I’m wondering if it would be beneficial for usability to have it work so that the reading ability will be in both, as now via Megapixels and can be separate As in, basic reader ability and the the other stuff as well via GUI.
The history option sound neat. From usability perspective, it would be nice to have a “re-do last code” button vs. “open list & copypaste”, if that’s not too much. On the other hand, there may be a need to edit the text (perhaps a typo in the original) before use/launch, as well as a need to turn that edited text to a new qr - close to what you have already in the plan.
If you’re looking for features to add, how about an optional visible/readable text below or besides the code. For instructions or content description or for and advert (maybe an optional default text) etc. It would save from copypasting the qr to an editor. Definitely something for later stages of development.
About the other plugins, I’m thinking those in terms of an easy way to transfer info (especially in a way that is pretty private and safe, if it’s via the phone camera from the screen of a friend or yourself). Especially strings that need to be correct (yes, like wifi pw etc.). How about a method of relaying the info for a quick access to shared screen or setting up shared secrets or relaying GPG? Custom codes sound good - could your app help set it up as a process, where a custom prefix could launch a designated app with the data or some other action(s)? One common one would be sharing contact details but there are several options: the plain text (with a nice layout - same row or stacked) or one of the virtual calling card standards.
And what about adding an encryption to the text? A bit overboard, but a simple pw mechanism might be useful for some. For a more advanced usecase, the pw could be replaced with location - as in: vicinity needed to open the qr (to prevent/inconvenience global use).
I think there will be limits that will be met and your GUI could help tell how much text/data can be crammed into the qr vs. size, or whether it would be smarter to think making the qr a link to the large text/data/file/object.
I hope these keep you busy. There are probably suporterts for a sleek, minimalist version as well.