I'll point you to the Osan'gar/Aran'gar intro scene too. Aginor specifically points out whatever Shaidar Haran didn't to cut their access to the Source, it wasn't like a shield and there was no way to break it.

It's not a large leap to make to speculate if Shaidar Haran can temporarily make it as if you were severed or had never had the ability at all, it may well be possible that Shai'tan can on a permanent basis (permanent only if he doesn't undo it, maybe) reduce your strength with some sort of TP shield.

I don't see anything in the books or quotes that eliminate this as a possibility.

If Jordan has left clues to puzzle out what happened to Cyndane (I'm not convinced he did, but maybe) then this might be it.

Cyndane seems way too strong for BA healing, I think, and it's unlikely she was stilled. If she lost her ability, it would be by being burned out, not stilled. It's hard to think any BA could better what Nynaeve did with her weave. It's hard to think why Semirhage would not have be ordered to learn the weave and do it. It's not like the DO to trust any channelling job to anyone but his Chosen.

As for the body theory, I find there's more holes in that one than swiss cheese. The fact Aran'gar can use her full strength in saidin in a delicate female body put serious dents in any theory like that. Sammal was short, but still very powerful. Alivia is the same. Nynaeve too. Even at lower levels, Moiraine was very small and delicate, yet she bettered any but Cadsuane in strength before the girls. Jordan never gave any hint that physique has any relation to strength. He spoke of genetics and soul as two factors in the ability, not genetics (specific determinant genes, not genetics in general) and additional body characteristics. By all evidence given Rand has the exact strength of LTT, strength is determined by the soul, and for the soul to be able to channel, the genes for the ability to develop must be present in the body the soul is incarnated in (the genes must be how the Wheel can enable or disable the ability to channel for everyone). Even the fact the bridge Nynaeve healed in Siuan/Logain/Leane was not something physical suggests strength is related to this conduit (it seems women's are made of saidin and men's of saidar - as if the opposite half of the OP (with the possible exception of the TP) is the only thing saidar/saidin can't pass through, an hypothesis supported by the method used by Rand to cleanse saidin : could his filter have been anything but saidar? I doubt it), not to anything in the body itself.