Some very interesting points and ideas! Just before I release King Philip's War I will make some further tests with the Pontiac scenario for the early Indian assaults against Detroit and Pitt and make some small changes if I think they are needed. I have a feeling that you may have got lucky as I have certainly been beaten back at Detroit a few times when attempting an early assault with a large Indian force (the Indians should probably never assault the larger forts for historical reasons but this muted change never made it into the game). But I want to make sure the balance is good and there is some danger that the Indians will suffer fairly heavy casualties sometimes if their assault fails. It hopefully is just down to the roll of the die and not a strategy that will always result in victory. Also was there time to send Dalyell to reinforce Detroit?
I love the idea about variable objectives to make a scenario more replayable! Obviously the main objectives would stay the same but some of the smaller ones could change a little. One problem is player understanding of this sort of thing. As with objectives disappearing, it can cause confusion. I think the Pontiac scenario could use an in-game event at the start of the game to highlight unusual things like this (also added to my list).
The small pox event poses no real obstacle since it doesn't strike as long as one keeps the units in smaller stack until the turn of the assault.
As Pocus once said to me - PBEM players - cunning sods (or something like that

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Thanks again for the feedback. It makes me very happy to know there are people out there enjoying the scenarios!
Cheers,
Chris