So I'm reading Unframed: The Art of Improvisation for Game Masters, since I've just started up an improv-heavy campaign. In the first chapter Robin D. Laws presents a method for resolving dialogue based on a character's intentions.
I've also had a tendency to appreciate reaction rolls but struggle with the "neutral" 6-8 range. Plugging Laws's approach into a reaction table makes for something immediately more gameable. I made some tweaks and here's what I've got.
(Before going on, I need to give credit to Courtney Campbell for On the Non-Player Character, which is also a big influence here.)
|The hell do these moose-guys want?
The Reaction Roll
Roll NPCs want...
2 Conflict (Armed or otherwise)
3-5 To establish their superiority (manoeuvre to their advantage, intimidate the party, etc.)
6-8 To advance their interests
9-11 To cooperate to mutual benefit (this might be a temporary alliance, a ceasefire, etc.)
12 To help (this could also mean surrender)
For unintelligent creatures, results above 8 should probably tend towards a deescalation of violence rather than cooperation.
All of the results above can be interpreted in relation to a character's interests - especially 6-8, where these are the determining factor in their behaviour. Every NPC and/or monster can be given a short list (say, 1-3) "interests" to pursue. (This is obviously inspired by Dungeon World's instincts.)
A giant spider might have: Protect its nest, trap prey, survive
Or a thief: Go unseen, steal valuables, survive
An orc: Eat ravenously, enslave the meek, fight to the death
A mercenary: Follow orders, gain riches, survive
A guard: Keep out interlopers, increase in rank, survive
A wolf: Hunt prey, follow the pack, survive
(Obviously "survive" comes up a lot.)
Apply a disposition modifier to reaction rolls based on an NPC's interests, where interests favouring cooperation grant a +1, and interests favouring conflict give a -1.
So if a party wanders into a thief's darkened stomping ground, the thief is going unseen, in a position to steal, and not in immediate danger. Therefore they have a disposition of -3.
If, however, the party catches the thief off guard and their treasure is well secured, the situation is stacked against the thief and their disposition is +3.
Some creatures that tend towards violence or cooperation may have a stacking natural modifier to disposition. An orc, for example, might have a disposition modifier of -2, making cooperation virtually impossible. Even if it's well-fed, and facing might enemies (+2), it still wants to fight to death and is naturally violent (-3), bringing its total to -1.
This can double as a loyalty/morale check
Rather than checking morale, you can keep nudging these modifiers and reroll reaction. In addition to the usual reasons to check morale, you might call for a reaction roll whenever the state of an NPC's interest has obviously changed. So if a thief has been attacking from the darkness until the players get a Light spell going, the thief can no longer go unseen and makes a reaction roll. You might end up with the surprising result that they offer to give directions at that point in order to get away safely.
Hirelings can make these checks too. Assume that "follow orders" or "get paid" are usually among their interests, but so too is "survive." When a situation presents a threat to their survival, you make one of these rolls to determine just how helpful they're willing to be. A hireling's loyalty can be represented by their natural disposition modifier.
The difference between a reaction roll and a loyalty or morale check is that the latter have binary "fight/flight" outcomes where as the latter allows for more nuance and dynamism without too much ambiguity.
Finally, it doesn't ask for much extra prep, beyond writing down a list of three things a particular NPC or monsters wants, one of which is usually "survival" anyway.