The guitar I mentioned in my last post came back from rehab. It took Dallas (the guitar repairman) a week, in amongst the other jobs he had on, but he and blind chance between them worked a minor miracle, because the Giannini is playable.
Here it is, cleaned up and with the correct low-tension nylon strings installed (backward, since I'm left-handed). The bass strings look metallic because they have a metal winding, but it isn't load-bearing; it's just to give them some extra mass and make them wear longer.
There's still some damage that either can't be fixed or would be too pricey to do anything about right now. Most notably:
The bridge is cracked and has started to peel away from the body. Both of these things are bad, but the good news is that relieving the overtension and installing the right strings seems to have arrested both of them - they don't appear to be getting any worse. We'll keep an eye on it. Worst-case scenario, the crack worsens to the point where the bridge can't hold the strings any more, and either has to be taken the rest of the way off and a new one glued on in its place, or possibly a separate tailpiece like those found on a lot of resonator and early solid-body electric guitars could be fitted.
It's not really obvious in photos (this one isn't my best effort), but the bulge in the top where the excess tension on the bridge stretched the wood is still there. There's probably nothing to be done about that, although it may settle back down a little in time now that the stress is off it.
The original tuning machines were destroyed, but the replacement ones are a perfect fit - and by some miracle, neither the headstock nor the neck broke under the strain of the metal strings. Most encouragingly (but hard to show in a photo), the neck mostly unwarped once the extra tension was off, so the guitar's intonation and action aren't hopelessly screwed up (as Dallas and I were afraid it would be at the start of this process). It'll probably always be a little off, but it's not like I'm player enough to notice it, let alone be bothered by it, at the moment. It works just fine as far as my fists of ham can tell. I can play "Pipeline" on it and everything. I know "Pipeline" is a weird thing to play on a classical guitar, but it's the only song I know at the moment. :)
It doesn't seem to want to stay in tune at the moment, but I'm given to understand that that's a new-nylon-strings thing, not a problem with the guitar. Other than that, we seem to have gotten incredibly lucky. Apart from the bridge being a little weird, it's in good playing shape - a perfectly serviceable student instrument.
The damage is still a Sad Thing that didn't need to happen, and I'd still like to give the person responsible a whupping, but it's a better outcome than either Dallas or I were expecting when we started. I'll have to be gentle with it, but then, you're supposed to be gentle with classical guitars anyway. That's how we got into this situation in the first place.