It could be possible to re add the open in menu. The only thing to make it so it passes the app review is to make it so that it can't accept anything that is in plain text or compiled python. Zip files are probably permissible because in nature they are not "executable code"
2.7 Apps that download code in any way or form will be rejected
The app wouldn't download code because it can not use the open in menu for plain text and compiled python.
2.8 Apps that install or launch other executable code will be rejected
Same as above.