Read this one with interest. Most of the points are valid, and relevant, the only one I want to pick up on is the one about the Alt being U/S so saving the battery. Understand clearly the why, and even the how, but it makes me nervous.
That's got the potential to put an unfair load on the controller. Yes, it may well be OK to fly in some airspace without radio on, the school I did my PPL at did it all the time, but then again, there was very little GA or anything else around, other than very low level MIL, which was so damn fast it didn't really matter.
Snag was, with some students, it encouraged a very lax attitude towards ATC, and in some cases, they then struggled big time when they did have to start to communicate with someone outside of the aircraft, as they were just not used to the extra workload. OK, that's a bit of drift, but relevant.
From the controller's point of view, to have an aircraft in and out of contanct could put the controller in a very difficult situation, in that if another aircraft comes on to channel, and it's clear that there's a potential conflict, if one of those potential conflict aircraft might or might not be in contact, what's he to do. Send the second one half way round the county just in case, or hope that both aircraft are truly VFR, and not doing anything that might make the situation tricky.
Maybe I'm being over fussy, but to me, it's better to have no contact at all, and know that's the case than to have a possible contact. Equally, if the aircraft is off air, then that's also adding to the situational awareness problems, if someone else comes up on channel with any sort of issue, the non radio aircraft is in the dark.
That's one of the things I hated about flying from the UK to the continent, in some areas, you lost the big picture because certain people insisted on using French instead of English. Fine for them, but very disconcerting for non French speakers, who were then placed in a position of not really knowing who was doing what.
So, while it's not illegal, or even an issue in some cases, it's (to me anyway) considerbly less than comfortable from an airmanship aspect, unless there's been a lot of preparation. To do something along the lines of "say nothing, that way there's no hassles" is not the sort of example I'd be comfortable about setting to a student if I was instructing.