That could be cool, for those willing to fork out some hard cash I don't know that I would buy them, because pewter minis tend to be more expensive than they are worth. Plus, you'd have to have some way of showing the damaged/undamaged strongholds.
Simple. Just like how you'd treat routed figures. Tip them over onto their sides! And yes, I have already ordered this game but not yet arrived at my place since I live overseas in Singapore and it's gonna take weeks to reach me. However, I have ALREADY gone ahead one step and bought the miniature castles. These are easy to find, and are DIRT CHEAP! And most importantly, the scale FITS perfectly at 1 and a half inch tall! The stone bases or pebbles at the bottom of the figures can be painted 4 colors for the 4 different factions (and the extra 4 can be painted for a 5th faction in case some people wish to use Hinnyboy's Dunwarr Dwarves (which I personally recommend as an add-on)
P.S: The shop is online and its name is Sunset Traders. U can easily find them on eBay. In case u are curious, they are going for a mere US$9.00 which gives u 20 such castle miniature pewters. This is more than enough since the actual game only comes with 4 strongholds each. (total of 16, u still get 4 spares for any breakage replacements!!)
Hope I managed to contribute something out there for my fellow runiverse mates, cheers!