My beloved T&T, in its 7th ed., actually don't have any moral rules. Many times lately I've found thinks lacking in this edition which was in the 5th ed. If there are any morale rules in 5th ed., I can't confirm it, since my copy is in storage. So I was thinking that maybe they wouldn't be so hard to make up.
Now things became more complex. I think it would be neat to only use d6, and base it on a SR like almost everything else in T&T. If it makes sense to consider morale when the own force have been reduced to half, the leader killed or maybe excessive amount of hits, we have a set of numbers that decrease. Also, when fighting a monster's MR will decrease. All these numbers decrease. It feels like they have to be considered, somehow.
The morale rating, what would that be? I'd like to base it upon something existing, so the system can be used with everything that's been published before. MR, level and Combat Adds are the components we have to use, apart from the stats of course. Level is usually not a very interesting number in T&T. Compared to D&D, it means little. MR and CA are both involved in combat, so maybe that would be something to base morale rules upon.
My first idea was to use the same mechanic you use for calculate dice of attack from MR, 1 + MR/10. Take that many dice and if any of them is a 6, you make your morale check and keep fighting. That mechanic has the problem that it's hard to figure out a way to account for lax troops and crack troops with bad and good morale, respectively.
My second idea was to roll a SR of some kind. Then we hit upon the trouble of determining the level of difficulty. Base it on level? Base on MR? Both have the nonsensical effect of making bigger monsters fail more often. I'd rather not bring in a subtraction, even though 10 - level might be a suggestion. That would of course have the problem that you'd have to scale 10 to the capabilities of the monster.
If you have any ideas how to sort this out, feel free to suggest them.