I'd be up for Invasions being more free form like rebellions are now, as victory conditions have changed in favor of writing good stories. I've personally enjoyed the rebellion format more because you're allowed to write to your strengths without everything being so regimented. I felt like I could actually write and roleplay. However, faction leaders should still be given advance notice of an impending invasion.
Going full anarchy is just going to promote even more metagaming and OOC nonsense that gets in the way of roleplaying. Popular members with large OOC clout would gain even more power leading to a situation of greater inequality as the whole map game can be dictated by few. This is the problem with anarchy. So then you're left spending more time wheeling and dealing in the background instead of being able to roleplay. Time is important to me, as I know it is to you. I don't want to spend it this way trying to enjoy a hobby.
This move would further discourage the creation of new and unique factions. If we did get any new factions, then they would just be franchises of preexisting ones like we're seeing right now. More members would just get off the map game entirely and stick to small and private threads.
We have mechanisms for factions and griefers to launch surprise attacks without warning or coordination, like skirmishes, rebellions, and public threads. As I said in an earlier feedback thread, Rebellions today are used more or less as stealth invasions between major factions.
In my experience as an FO, coordination and talks, even it's just some advance notice of stuff about to go down, goes a long way to stem toxic behavior that ruins the roleplay experience. By taking steps to promote more civility on the OOC front, instead of trying to destroy it, then maybe you would see a more dynamic map game like you desire.