The problem is maintaining the data that identifies which channels are on which mux. This would require the exact transmitter and the channels it carries for every user as this would not be the same for everyone. It's relatively simple to do this on the box because it has access to the actual database files with this information. Any solution would require a daily comparison of the current data to identify changes and that's only the first step.
To some extent this capability exists on the Foxsat-HDR (it's much easier on satellite). I have a Excel application that runs from a data table on a spreadsheet with the required data for each channel on it. Only a few channels require modification for a specific postcode, these are relatively simple for a user to edit, as the Foxsat has an easy way to check the current transponder for the few channels that have a different transponder to my West Midlands postcode.
A package available for the custom firmware for this box can create a full channel database for my Foxsat every day. It can compare any changes overnight and report by e-mail any changes to this data.
I can then easily edit the worksheet data with the data on it and upload it to a file sharing site. The application then allows a user with Excel on a PC to identify which 3rd channels can be viewed for any recording combination (using VBA). and also is able to identify if a specific 3rd channel would be available by choosing an alternate recording source (BBC 1 SD has regional sources on both horizontal and vertical transponders).
Random example of change e-mail
Channel Changes after the 3:00am Housekeeping on Monday 22-08-2016 to today's (Tuesday 23-08-2016) 3:00 am Housekeeping are:
No Name ServiceID PMT VPID Audio PCR Subs TText Frequency SymbolRate Polarity
--- /opt/webif/plugin/SatInfo/beforeHK.txt
+++ /opt/webif/plugin/SatInfo/afterHK.txt
@@ -78,16 +77,0 @@
-261 BBC Olymp 1 HD 1081 256 512 660 512 8192 8192 10744 23000 H
-262 BBC Olymp 2 HD 1082 257 513 661 513 8192 8192 10744 23000 H
-263 BBC Olymp 3 HD 1083 258 514 662 514 8192 8192 10744 23000 H
-264 BBC Olymp 4 HD 1084 256 512 660 512 8192 8192 10862 23000 H
-265 BBC Olymp 5 HD 1085 257 513 661 513 8192 8192 10862 23000 H
-266 BBC Olymp 6 HD 1086 258 514 662 514 8192 8192 10862 23000 H
-267 BBC Olymp 7 HD 1087 256 515 660 515 8192 8192 10876 23000 V
-268 BBC Olymp 8 HD 1088 260 516 661 516 8192 8192 10876 23000 V
-271 BBC Olympics 1 6390 262 5400 5401 5400 8192 8192 10773 22000 H
-272 BBC Olympics 2 6802 256 5100 5101 5100 8192 8192 12421 27500 H
-273 BBC Olympics 3 6803 257 5200 5201 5200 8192 8192 12421 27500 H
-274 BBC Olympics 4 6804 258 5300 5301 5300 8192 8192 12421 27500 H
-275 BBC Olympics 5 6805 259 5400 5401 5400 8192 8192 12421 27500 H
-276 BBC Olympics 6 6806 260 5500 5501 5500 8192 8192 12421 27500 H
-277 BBC Olympics 7 6807 264 5600 5601 5600 8192 8192 12421 27500 H
-278 BBC Olympics 8 6800 265 5700 5701 5700 8192 8192 12421 27500 H
@@ -228,0 +213 @@
+981 BBC RB 1 6390 262 5400 5401 5400 8192 8192 10773 22000 H
Clearly the recent Olympic channels being removed.
TBH I think even this halfway stage would be hard (near impossible) because of the much larger channel combinations you have on Freeview down to different geographical locations. UK satellite boxes can get all available channels, freesat channels not on your epg. still exist on the box database (they are merely hidden).
The Foxsat-HDR CF channel editor can add them all to your epg which is impossible to do on a Freeview box.
This gives me a light bulb moment, if I add all of them to my box, my daily e-mail may find them all (even ones that I don't use).
More experimentation required