you can always try the plastic bag + vacuum cleaner trick - take a thin flexible rope, tie it to a small plastic bag, stuff the small plastic bag into the conduit, use a vacuum cleaner at the other end to suck the plastic bag & rope through. You can then use the rope to pull through new cable. If you make the rope twice the length of the conduit, you can keep it in there indefinitely to pull through new cable whenever you want.

Fair enough! I had a cursory search in the post for mention of conduit and couldn't see anything obvious so wasn't sure.

AFAIK fibre cable should be pretty flexible, though not a massive fan of tension.

From memory bends shouldn't be less than 5cm radius or thereabouts so it depends on your conduit size!

Nice post btw, appreciate the detailed planning involved.

I've seen dummy wires being put in when the conduit goes in.

Say initially you need 2 wires from A to B. That probably means there's plenty of room left. So you just put 4 more other wires in there. When the time comes you need to pull a new one, you pull in the new by pulling out the old

That's why they invented cable lube. That number of turns is no obstacle, even with existing cables. But you should also have a pull cord spool.

Bends ideally need pull boxes, but given the lack of pull boxes, you might be able to use fish tape where where fish rods / glow rods don't work, if you cannot get a pullstring / pull cable going.