That would be cool, having interpersonal relationships influence the decisions. If a dwarf has a good friend, lover or infant (and isn't actively using it as supplementary body armor), that wasn't in the bomb shelter burrow yet, they'd lay down their life to buy time, but if they're some new migrant soaper who hasn't even sampled the fort's booze yet, they'll shift quickly into "fuck this fort" mode and scurry for cover. There was a good Wavinator post on GDnet a while ago about really awesome feats being triggered by a character's social situation, so a soldier with the "girl waiting for me back home" tag could rally and survive incapacitating wounds or might endure starvation more robustly than his base stats should indicate. A newlywed dwarf with a pregnant wife might get a one-time bonus to pain tolerance or a chance to recover from a nervous system injury due to his upgraded "will to live". A whole list of triggers could be linked into this, so a famous warrior mother, or a noble lineage, or having bootstrapped from eating vermin to living in a plush room through his industry might all have the same effect, but for different reasons.
On the more general topic of "epic last stands" as Umi pointed out, maybe each military squad could have a configurable "strictness" rating, similar to the setting for the minimum number of dwarves on-station, and a higher rigor would hurt morale and require better leadership attributes from the squad leader, but would make the squad hold its ground longer in the face of a losing battle. So you could either hand-pick an elite squad with a great leader that would really hold the line, or you could just flog your recruits and get good performance out of them at the expense of fort happiness and the risk of tantrums, mutinies and "friendly fire" incidents against your officers.
On a related (barely) note, I would like to see some emigration from the fort. When a caravan packs up and heads to the next stop, the more miserable or disenfranchised members of the fort might have a chance to pack their socks into a backpack and move away. Give the dwarf a vague understanding that staying in unacceptable conditions would inevitably lead to insanity and death, and let them act to mitigate that risk.