It's a very difficult position to be in, but really little different to when the property prices crashed in the early 1990s in the UK.
The boom and bust then, comparative to today, turned round very quickly - taking the whole of the UK into consideration (although it didn't affect Scotland because the bust came before they boomed!).
We didn't lose out, not in equity, but we certainly lost out on the interest rate situation despite the fact we didn't overstretch ourselves when taking out the original mortgage. But ours took - I think 3 years to sell and we have a grand total of 5 viewings.
During that period, when we couldn't sell, we went to look at a variety of properties that I would have killed to buy and the prices were ridiculously low. I think one was around the 30k mark - asking price. A farm house that needed renovation in a beautiful setting. They couldn't sell it. Nothing was moving. Buyers market.
I saw that farmhouse sold a couple of years ago for nigh on 750k.
What you have to do in such situations, is forget what you paid for it. Forget what it has cost you in renovations. Forget about it as being an investment and consider how long you have spent in it as a home (if indeed you have)
Consider that you bought at the wrong time and at the wrong price.
Then look at what IS selling. Similar properties in your region. Look at the price and target accordingly.
I'm not being cruel, nasty or hard - I've just been in a similar situation.
It may be that in France property prices suddenly shoot up. But not unless they free up lending in France like they did in the UK, because that was the only thing that made that market boom. They may, of course, discover oil, gold, or whatever in your region, but that too is somewhat unlikely.
The other options are doing exactly what the OP is doing and investigating other possibilities.
Remember that a lot of people who are in France today, came here back in the early 1990s precisely because they lost everything in the UK due to the boom and bust.