Here's what I could work out from your list:
Beosound 4 - no detailed enough info in service manual (ask the dealer)
BL4000 - the main transformers would need replacing, standby transformers can be rewired
BL6000 - can be rewired with no component changes
BL3500 - all new transformers needed, probably not feasible
Beolink Active - apparently very easy to rewire
I
couldn't find relevant info on the PC2. See the type sticker, if it
says "100-240VAC" or something it can be used with no changes.
Anyway, the link boxes and possibly BS4 as well need so little power that you could run them through a step-up transformer. The BS4 might have issues with FM radio though.