1. I manage deletions this way:
a. For News, Current Affairs, and any other regular show that is only important for a short period, I use the Retention settings in the Recording Rule to automatically delete the program after a number of days, or to retain only a specified number of programs. This works well. For example, I keep a week of a nightly News show, as I may wish to go back and watch a story for up to a week. After that, the News program is pretty irrelevant, so I have MC delete it.
b. For once off recordings that don't need to be kept, I watch them and then delete them immediately, through Theatre View. I don't find the process onerous to do so, since it is just one recording.
c. For Series I usually keep the recording for some time. At least for the whole Season, of not longer. For some Series I keep all Seasons until I no longer want them. Like CountryBumkin, I have the storage space. When it is time to delete them, I do it in Standard View, where I have better visibility of what I am doing, and I can delete a whole Season, or a whole Series, with one press of the Delete key, and then a confirmation. I consider this a maintenance process, so I just do it every now and then, and Standard View is the best way to do this.
2. I love it that MC returns to the list of shows in the Series/Season after I finish watching an Episode. I wouldn't want it any other way. I often watch more than one Episode of a Series, and I want to just press the Down (select the new episode), Ok (review the episode description), Ok (to start playback and watch the program) keys to watch the next one. Even if I don't watch the next episode, I might scroll down and review the description of the next one. The current functionality is convenient.
3. This may be a convenience, but honestly I just drill down from Series to Season to Episodes, and I can see how many recordings are in there. In fact, I don't really like that MC will jump from Series to Episode if there is only one Season recorded so far, since I don't step through the Seasons and therefore don't see the Season listed. But that is a minor issue, as I can see the Season.Episode number in the list of recorded programs.
A one button delete should be possible to set up on a programmable remote. Do you really want to have that power on one button though? I suspect you would still get a confirmation question though, so I guess it wouldn't be so bad.
This thread has reminded me of one thing I find annoying though, and that is scrolling through 16 Seasons of CSI, or 11 Seasons of Criminal Minds to get to the current programs. A reverse (Descending) sort of Season number would be better. . . Done. Much better now. Isn't MC so flexible!