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I think for both options you need to be clearer about the modifiers (although I get this may just be sample wording). Even if the modifiers are rare, its better to have them spelt out.
As there is the possibility for several simultaneous modifiers, Option 1 seems by far the best. For option 2, you would have to spell out all possible interactions (i.e. normally 7+, if X 6+, if Y 5+, if Z 8+, if X and Y 7+, etc.). 1 is much clearer and allows you to flexibly add new modifiers or alter the base stat if desired.
I prefer option 1. In our games we also allow certain commanders who are unpopular and/or distrusted to have negative modifiers for discipline as the command structure is less likely to follow their orders. Others have a negative effect on morale very few have both.
If the ruleset is for some specific genre like historical medieval warfare, the option #2 is better by allowing players to learn the rules by heart. Description suggests this choice.If the ruleset is universal with warlocks and robots, option #1 is better as long as any of modifiers are taken into account before any dice are rolled. For to imaginarily modify a visible dice score dulls the players' excitement of the roll – gods decide the tin soldiers' fates through the dice scores and that must be honoured!
If I were going with a fixed morale number, I'd set it between seven and nine, and then each unit's leadership would be changed from a number to a modifier.Instead of a unit being "Leadership 6", they'd be "Leadership -1". A bog standard unit might be Leadership 0, a veteran unit Leadership +1 or +2, and a rabble or militia Leadership -1, or -2. This would slot in with the officers giving bonuses (and I'm a big fan of involving poor leaders in games, but that's just me...).
Interesting in your take on morale levels, I’d have thought with militias and levies at one end and knights at the other there is plenty of scope for better and worse morale levels. Although in any given game most units are likely to sit in the middle, but it can be an interesting challenge to pit more lower level units against an elite force.