Pretty much completely agree with you.

1.) Parties, prioritize this please. Exping in a group in any way would be so much nicer.

2.) Partying with Adventurers, could be fun, and I'd even accept the probably necessary rule of (One monster in the party = No loot other than crystals and seals for anyone.) While I get that it's neat and flavorful for a Beastmaster to be linked, I think ultimately this would just be a pain and don't think it should be required.

3.) A thousand times this, reward adventurers better, reward monipulator's "main characters" in some way for doing all the monster levelling, I know this system is meant to be and end unto itself, but it doesn't feel like it should be. I put forth a "Monstrosity as Merits" idea before, but a gear reward would be acceptable as well.

4.) I think this is a good idea, to those saying the playing field would be imbalanced, it already is.

5.) In addition to quests or BCNMs that can only be done as a party of monsters, that drops perhaps "matching" rewards, (For example, I kill a Bugard in a Monster BCNM, it drops some loot that we all lot on for our adventurers to use, and we all obtain some Instinct for beating the battle.) I would also like to see Monipulators available to participate in more content.