* Idea 1
Create a "cron job" or "at job" that does updates up to the minute and make those images current...and local--and the cron job can auto-delete the temp file later or back it up
* Idea 2
Make an elisp .el program that gets loaded and run whenever you open the .org file with the remote image...and that code updates the images locally
* Idea 3
Use the patch you reference and create your own .el program that gets loaded and run when you want it--a cursory examination of the patch reveals that it depends on ImageMagick which is great software that everyone should use; but, it's a dependency that is NOT emacs software and so it makes sense that it was never put into the main OrgMode software tree
P.S. I created code and methods to put and run animated .gif's into OrgMode buffers and run them, it was amusing; but, it wasted a lot of ram and slowed everything down
Emacs and OrgMode do many great things; but, the focus has always been, at it's core, the most powerful editor and stateless organizing software--it's not a browser of dynamically generated Internet pics--Emacs W3 was created to do that, and it hasn't been updated in years--suggest you look at Emacs W3 browser code and/or w3m browser or even UZBL browser--all of which were made into good extensions for doing such things--UZBL by the way has been made to operate fully encapsulated in an emacs buffer