I have one of those original Kapp drops.
The Halo is a great hopper that will force feed and prevent chops. However, even that one has issues when you run the hopper out of paint in the heat of a battle. That is when you need the level 10 to prevent a chop. I would recommend a level 10 bolt on all mags that don't have eyes. If the valve has a phase 2 venturi bolt, then I would invest in the level 10 upgrade for sure, no matter what..
If you want to shave weight, put a dovetail directly onto the bottom of your frame. You can still use the Kapp on-off, but it will be a lot lighter. You don't give up that much tightness in your setup. Its just different and will actually allow you to shoot from a more stable platform. Get rid of the sight rail. It adds a lot of weight without much function. There are lighter trigger frames, but if you like yours its ok, because you can shim the trigger for a more crisp feel. The rest won't save much weight unless you get a full ULE body and cocker barrel. The phase 2 valve should be fine. You can change the on-off, but if its working fine it doesn't need to be upgraded.
Except for the Automag in front, its usually the man behind the equipment that counts.