Looking at the army generators in the ECW rulebook, it provides a generator for Hopton's army at Cheriton in which all infantry are shot-heavy, as an example of the West Country theatre. However, as the description notes, this was after Hopton had made his rendezvous with the Oxford army and had been given fresh troops and re-equipped. I'm thus wondering if the Cheriton generator is wholly appropriate for earlier battles in the West Country campaign.

As the book indicates, Lansdowne was an anomaly because pike and shot were separated so that probably needs to be handled by a scenario. But I wonder whether for Stratton and (Hopton's part at) Roundway Down it would be more appropriate to use the Edgehill infantry generator, so that mixed units are a possibility, or otherwise tweak the infantry generator from Cheriton.

I must admit I'm not sure what the equipment status of Hopton's army was like before it arrived at Devizes, but I can't imagine it was as well-equipped as the contemporary Oxford army. Maybe I underestimate them though.

Pretty valid reasoning all around.   The regional ECW armies were generally ad hoc forces put together temporarily and fluctuating through losses, reinforcements, garrisons etc.  It was rare for any continuity to be maintained.   This can be exacerbated as I chose to base the lisitngs on a single action.   So yes, feel free to mix and match on the generators as you see fit.

If you think this is required for the West Country, just be glad you aren't doing Montrose's campaigns.   His little force changed wholesale from action to action - never the same twice and with wildly varying compositions.  You need a seperate generator for each action!