Creating status effect that scales on the number of allies with a specified condition

[Cmushi]

I am trying to implement an ability similar to Brilliant Tactician (grant status effect to self if all allies have specified condition) but with a scalable status effect that scales on the number of allies with a specified condition instead.

I usually try to find a similar ability that already exists ingame and tweak it but I cannot find any except for Brilliant Tactician being the closest.  I might be wrong but Brilliant Tactician seems to only trigger on if all or none condition and cannot be tweaked to for each condition.

If I have to create the ability from scratch:

• Create an ability aura that affects allies with a specified condition
• This aura grants them another ability aura that affects the original user which grants them the scalable status effect 

The problem that I notice is that aura can only grant status effects and not abilities and I am unsure if there is way to create ability granting auras.

[Cmushi]

To add more context, the ability grants +1 engagement for each non engaged ally.

I think I need to create 4 variants* of the ability using IsEngagedByCount(Guid, EqualTo, 1-4*) as activationConditional to scale it with the number of non engaged allies.

Does IsEngagedByCount count the number of engagments of Guid or the number of Guid that are engaged?

Whats the difference between PartyAll and PartyAny as Guid in IsEngagedByCount?