While I haven't used ratchet rakes, I think that it'll depend on the nature of the "light grading" being done. While digging/breaking soil can be done with a FEL, they really aren't optimized for it but really do better with handling already loose bulk material - or other types of material handling tasks with the appropriate implements.
Personally having come to an immediate & complete dead stop while using a box blade before (got caught a rather large root with the rippers/scarifiers) I'd say if/when digging/ripping soil with the FEL (using bucket or
grapple) knowing what's underground is even more important than it is with 3pt implements - just to avoid inducing side loads on the FEL. Even if no permanent damage is done to the FEL when a side-load is imparted to it the experience it can be a rather unpleasantly unforgettable.
Something to consider with the subsoiler/middle buster would be how deep you're wanting to go (along with where/how you'd use it) since the rippers/scarifiers on a box blade can used to good effect (without dragging soil along) if the box blade is tipped fully forward and the rear cutting edge isn't permitted to make ground contact. Did that last spring to create planting lanes in my garden since I didn't have any other quick method of laying out parallel lines for hand-planting.
A carry all can be a very useful implement (finally got around to ordering one for myself even though I have pallet forks, and buckets for the FEL) since the platform built upon it can be customized/replaced when needed. It also keeps the objects placed upon it behind you -- which can be rather nice when driving forward since if an item falls (and you don't see it) it won't be driven over -- and unlike with a bucket carried objects aren't as likely to be "out of sight out of mind" when you try to scoop into a pile with the loader.
When I get mine and build platform on it, I'm planning to bolt a 2" receiver hitch plate to the bottom of it (probably run some additional support across the bottom to help distribute the loads as a "just in case" even though it's probably overkill for light loads) so I can use it for some trailer moving ...and take advantage of all the other 2" receiver tools/attachments that exist. Will potentially add a set of casters so it can more easily be moved when not on the tractor as well.
Just my thoughts though....