About current capability: What georges80 said - they will not stand the current directly and besides, the ones I know of has way too high resistance for that.
I don't know what is the size of nFlex or bFlex or maxFlex, but many standard IC converters, with only a very few and small external components, adjust voltage* by two, or even one resistor. In the place of that resistor you can put a force sensor, they can be really small, less than a mm thick.
So the cirquit can be made really small, I am putting one into an arc AAA now, and found that even with a thick copper sink and a huge inductor I had more space, so I am waiting for some tiny smd 0402/0603 battery indicator LEDs. It is a bit of a mechanical challenge though and I am not sure yet if it will work inside the light - but the test cirquit does.
I don't recall the cycle life but it wasn't horrible I think. The lusense ones had a few cm leads that I could not cut off since I was unable to connect reliably to the stumps. No problem with the ones digikey carries (solderable leads), but those are a bit more fragile. The black antistatic foam used when packing IC's also has the property of reducing resistance when compressed, but it has a sort of shape memory (won't expand fully after severely compressed) so I think it is not suitable.
For my application I could otherwise use some tiny reed switches (reacts on/off to magnetism), or maybe a linear hall effect sensor (reacts continously to magnetism), though I didn't find a suitable one yet.
*I don't need current control, current will be limited by the converter itself or by a PTC thermal resistor in series with the force sensor. Besides, I size the resistors for the specific LED's Vf.