The occultist is one of the few non-level 9 casters who can pull off possession by level 10 and greater possession by level 16. So far, so good.
But... An occultist needs to hold their implements to cast spells (and for just about any other power). So when possessing, they'll first have to loot their own body to regain access to their class abilities. While this is crippling, it is comparable to a wizard having to loot their own spell component pouch. It's also circumventable by playing a battle host with a called weapon. One swift action and all is yours again.
But greater possession doesn't have this luxury. Once cast, your body is gone, so, presumably, so is our weapon. This makes greater possession, while clearly meant to be cool for an occultist, a horrible choice!
1 is this likely to be intentional?
2 can you drop a weapon as a free action while in the process of casting?, because that would solve it for at least the battle host.
3 Do items with a continuous effect still work when using greater possession? Or does that headband cease to give its +6 int suddenly?
I think it is intentional.
At 16th level the spell casting concentration checks aren’t impossible, but the CL limit hurts and I don’t think you can use your focus powers. One option would be to drop all implements except Necromancy before casting, but that gives you big risk and problems if the spell ends in an uncontrolled way.
I highly doubt it was intentional. Just unfortunate.
When it comes to possession the new bodies is treated as your own. You ignore all magical items on your own body and would if the new body was wearing magical items you would gain their benefit.
As to the downside it's not really that big of a deal.
Possession or greater possession, if your intent is to continually use the body then the former just requires you store your body somewhere safe.
Offensively greater possession is better, you are using it more to take out a bad guy mid fight without the risk of being killed, you won't be as concerned with looting your own body.
Not super sure how Occultist Implements work, but does this solve your problem?
Receiving: You can prepare an object ahead of time to apport it to yourself by casting the spell upon it and assigning a mental trigger to complete the spell. You don’t need line of sight to the object to apport it to you, but the object must be within a distance equal to 25 feet + 5 feet per 2 levels. Completing the spell is a swift action that has the same restrictions as a thought spell component.