Wacky Idea (warning: opinions contained within)

[Knjaz]

On-death repair costs are pretty simple to do (without flhook magic).

Make Nanobots & Shield Batteries cost somewhere along the lines of 10,000 credits each.
Snubs would have a ~1,000,000 - 2,000,000 credit death penalty (which is, to be fair, negligible).
Big capitals would have to pay up to 44,000,000 credits in repair costs (Marduk).

That does leave Cruisers as fairly cheap, though, and might cause some issues with NPC nanobot farming (although they could just be removed from NPCs entirely).

We need more money sinks in Disco so that players have initiative to trade. Right now, I don't trade (much) as I don't have any pressing need for a ship, and keeping ships stocked costs almost nothing.

Well, with this, you'll be paying ~6-8 millions for a gunboat, 13-16 millions for a dead cruiser, or 8-13 for a dead transport/liner, in addition to the cargo you've just lost to piracy. (well, there's always an option to fly without bots, but still).

Although, aside from transport problems (fixable by moving their hull points from nanobots to the hull itself. Drawback - no/very limited bot trading in Convoys) and the fact that it kills RepShip... yes, it actually has some chances to work, but only if above mentioned things, as well as battleships flying without useless shield batteries (and overall difference in cost-efficiency between nanobots and batteries) would be addressed.