As you've already figured out, Ara, trying to do full-blown Zone System work with roll film is tough. With the Hassy, you either need to spread your exposures between (appropriately-marked) magazines, or opt for an alternative approach that isn't quite the Zone System (but might be just as effective in producing good images). I would also point out that a total of 3 magazines only covers N, N-1 and N+1. If you encounter an N-2 situation, you're stuck.

I would agree with the observations of others - if you're going to meter small areas of a scene, a spot meter is convenient, if not essential. At a distance, even a 1 spot can be wider than needed to isolate individual tonal areas.

Personally, I use a combination of incident readings and spot readings with a Sekonic L-508. The incident reading tells me what the exposure would be to render everything at its "true tonality", and the spot readings tell me where individual areas would fall in relation to the film's ability to capture the luminence range of the scene. Once armed with that information, I can decide how I want to approach the exposure, and whether I want to try to compensate with a variation in the development. That decision is much easier with sheet film, of course.

If faced with your situation, I'm not sure that trying to implement the Zone System is really practical. I think I'd suggest just continuing to use incident readings, and taking more pictures - perhaps bracketing a bit (+1 stop, -1 stop for B&W film) for important shots, but staying with "normal" development.