The place to start would be to change the activities required from mainly being hauling from A to B, which is hardly a challenging activity in itself. If you're not opposed its not challenge at all. If you are opposed then either its incredibly one sided if you're not kitted for being attacked or its a cakewalk if you are.
Make the activities themselves challenging, regardless of whether other players are around or not might be a better starting point. Timezones, platforms, size of play area, instancing, all conspire against people getting challenging gameplay from Powerplay, even in some sort of open only utopia.
Powerplay missions for merits might be one solution.
I thought along the same lines with these:
This one is a 'middle ground' between something new and what we have: https://forums.frontier.co.uk/threads/powerplay-in-solo.565581/page-9#post-8961161
This one is much newer: https://forums.frontier.co.uk/threa...-to-allow-power-collapse.586689/#post-9427332
Timezones have never really mattered (otherwise merit bombs would never workTimezones, platforms, size of play area, instancing, all conspire against people getting challenging gameplay from Powerplay, even in some sort of open only utopia.