Not tried this, as I have no offsets to check against at the moment.
But a few tweaks will be needed. And yes I know this is very new and tweaks will come.
Firstly I am confused why it would take 10-60 mins to perform the text swap? Even with a large provider, it shouldn't be that slow.
in xmltv.sh your are looking for +0000 - It won't always be +0000, depending on provider or where it has originally sourced its epg from. Could be +0100, +0500 etc.
sed -i '/+0000/ s//time/g' /media/hdd/epg/iptvepg.xml
you seem to be gzipping this after its finished. That shouldn't be required. The xml would be fine to read.
This is a local file, so probably no need to compress. Unless you are doing for space saving
Why are you creating new epg source files. You can use the exisiting source files in epgimporter folder, and change the url reference in there instead to the local xmltv file rather than the external url ref. As long as the script is run after jedi update this will not be a problem
That way you will not run into issues with multiple providers.