How does everyone store their internals to reduce risk of damage? For example, shock mounting.
I tend to store my batteries and electronics, in the Featherweight class upwards, in a Tupperware box that is padded out with a few Sainsburys shopping bags. The box itself is then held onto the HDPE chassis plate with bolts and in the past, I've used the fuzzy side of Velcro to add further shock protection.

How strong do you think the chains would need to be to resist hits against opposing weapons, such as spinners. (Keep in mind we're mostly attending Extreme Robots events, so spinner speed is limited.)
If this is a concern, I might consider doubling up on the chain so you'd have two strands doing the same thing al la Carbide. However, so long as the chain is well tensioned and a cover guard fitted so as much as the chain is hidden, you should be OK. I would however defer to one of the Axe featherweights on this one though, such as BattleAxe or Hatchet since they do use chains in their weapon so far as I know.

Alternatively, a pulley and belt might be simpler to add and maintain?