This is already available.
1. Create a new Theatre View view under the Guide group. I created one called "Guide Filtered".
2. Go into Theatre View, select the "Guide Filtered" view. Press the up arrow to highlight the view name, then the right arrow to select "More". Select "Toggle List Style" until you get the grid layout.
3. Now comes the hard part; Work out how to identify the channels to include on the list, and then go back into the Theatre View view maintenance and enter whatever is required in the "Set rules for display..." for the view.
I tried a couple of simple examples that were partly successful. Adding a Keyword to a channel via a Channels Smartlist didn't seem to work. I added the Keyword "Filtered" to a few channels, and then tried the rules [Keywords]="Filtered" (contains), and [Keywords]=[Filtered] (is), and various filters on [TV Channel], [TV Channel Number], [TV Tuner Input Type], and [TV XMLTV ID] and didn't have a lot of success. But that is just me not getting the filter right, or understanding exactly what data is available to use as a filter in that view.
With some help, I'm sure that various Guides could be set up.
One way to see what is going on is to set up a rule that says "'TV Channel' is ' then you get a drop down list of the internal TV Channel identifiers. From there I was able to add several channels,
with one rule for each channel, and have them display in my filtered Guide. The rule, as seen in the "Import/Export" window, was;
([TV Channel]=[23429] or [TV Channel]=[23431] or [TV Channel]=[23432] or [TV Channel]=[23435] or [TV Channel]=[23436])
So as you can see, the TV Channel numbers aren't human readable, and need some interpretation. Not a huge huddle though.
Works great try it out.
EDIT:Actually, the "Favorites" Guide is an example of what dejwi is asking for. I just had a look at the "Favorites" Guide settings, and it shows how to select channels using a Keyword. The rule required is;
[=TVInfo(ChannelKeywords)&DataType=[List]]=[Favorite]
Replace "Favorite" with any keyword you want to group channels by, and the job is done. Well, once you tag all the channels with a keyword. But that could be streamlined using a smartlist or custom view to find and select a a range of channels, then tag them all in groups. Large groups I hope when there are 2500 channels to tag.
Simple when you know how.