if I was flying a glider I would buy a Mode C transponder and install it, and to hell with silly rules for certified aircraft.
The CAA is currently running a programme of glider checks, so there's at least an appreciable chance that you would, at the least be grounded. My guess is there are also criminal penalties.
The weight and
balance issue is critical for some gliders, and don't forget these are single seaters, not four-seat aircraft, so the margins are tighter. Space is generally more of an issue, especially in the panel. Don't forget that weight includes the batteries to run the thing, and that's where the problem often lies.
I'm booked for another week of glider flying lessons next week at a club in the Netherlands. All their gliders have a mode-S transponder fitted. So don't tell me it can't be done because of weight, panel space, electrical requirements or certification issues.
Maybe true of the Netherlands, but try this with the CAA - the certification issues are very real. I believe that most Dutch pilots who do more than short local flights do them in Germany, and I imagine they simply turn off the transponder once across the border, thus conserving power. There is one model only which might conceivably run for, say, 6 hours from a standard glider battery, assuming there is space to fit an extra battery. 6 hours is not an exceptionally long glider flight.
I agree that there might be some types of (older) gliders for which one or two of the problems you mentioned may be insurmountable, but that's certainly not the case across the entire fleet.
It's currently true for about 90% of the fleet (my estimation). I'm pretty sure it's true for 100% of the gliders at my club. To be fair, not totally insurmountable - I could pay the manufacturer to produce an installation scheme for my glider, then pay the CAA its minor mod fee, then pay for the instrument and installation. I don't think I would see change from 5 grand.
But the main issue I have to agree about is the cost/benefit issue. You can get an old wooden glider (in good condition) for less than 10 grand. Spending 2 grand or more on a transponder installation is a lot of money then. But how often do these old wooden gliders really leave the vicinity of the glider site? I'm not too worried about them flying around without transponders. It's the high performance gliders that fly competitions all over the place, sometimes in dense packs, that I'm worried about.
You're out of touch on prices - an old wood glider runs 2-4 grand, and much of the glass fleet is in the 8-15 grand range - and those glass gliders go long distances. My sub-10 grand glider is perfectly capable of a 500km glight, though I haven't managed one yet.
Cost is a real issue - my costs of sole ownership, including flying costs, are in the region of £2,500 per annum, so installing a transponder is likely to cost me 2 years worth of flying. A second-hand mode C might be less than a grand installed, but the CAA won't allow that. And anyway, I'd have to leave it turned off most of the time, only using it when near controlled airspace, because I can't carry enough batteries.
Returning to the notams issue, I agree that the level of clutter is so great that the usefulness of the whole system is reduced. Checking the notams for today, of 177 there were only three which were in any way relevant for glider flying within a 100nm range of my airfield.
The major gliding competition notams seem to me to be potentially useful though, because between 50 and 100 aircraft will be launched and will hang around the vicinity waiting for the start gate to open. That's probably worth being aware of and avoiding! Once they're off on task the notam tells you nothing worthwhile about where to expect them, and the reasons why have been explained earlier.
This thread started with a nav warning notam - some replies seem to think that a warning is much the same as an RAT. I'm never going to fly through the middle of an aerobatics competition with such a notam (unless I've missed the notam somehow), but I do have a perfect right to do so if I comply with the rules of the air. It's just a warning to me that there are extra dangers there, and to be careful. I won't do it because I always try to comply with my wife's instructions: "Fly nicely".