pdh, just wire the lights initially so that when every light switch is down, the lights are off. You may end up with some up and down during normal use, but during a power failure, put them all down, and you'll know the lights will be off when power returns. And, honestly, this doesn't even sound like a problem so much as an aesthetic preference and pet peeve- for anything actually critical, you should be securing the breaker and not relying on light switches anyhow. The electrical costs for a single light are negligible in the scheme of things, especially considering the low-likelihood of the kind of thing you're talking about. I mean, you're talking about 10 cents a day for a 60W bulb left on 24/7. About $1/month for a typical CFL. I have a bunch I just leave on 24/7 intentionally because.
The reason I would turn them off has nothing to do with the reason I would secure a breaker. I never rely on switches to make a circuit "safe" for wiring work. It's all about making sure lights are off ... or on as the case may be. I can make a light be on by moving all switches down to off, then moving one back up. Then when I come back, if the power is back on, the lights should be in the desired on/off arrangement. FYI, I have 500W of nice warm kitchen task lights on one of the 3-ways (each end of access to the kitchen). CFLs are unsuitable for task lighting, at least for me. My electrical conservation is in the form of not having lights on unless I need them.
3-way switches are indispensible, especially for rooms with multiple entrances. I have 4 light switches controlling my dining room chandalier, and wouldn't have it any other way. One of which is a push-button, boo-yah!
Switches that do up and down momentary contact, resting in the middle position, controlling a contactor/relay, would do the job. I would prefer this kind of setup.
