Access world or arbitrary data through world based on callback

[ZweiEuro]

Hi!
I want to try and access the entire world through its ReadComponent interface via a callback.
My plan was to attach a InputHandler to my entity and with a list of triggers. should the input system see a trigger as pressed, it should call a generic callback that does whatever the callback wants to do.
By design this means I cant tell from the get go what components are needed inside the callback.
Giving the system an Arc is also not in the cards as far as I can tell since I need the &mut World after the system has been instanciated.

Any idea how I can achieve this? or is this too much against the nature of an ECS?

[Imberflur]

At least using specs, to achieve this I would have the input handling be an independent function (rather than an ecs system) that you pass the whole &must World to.

[ZweiEuro]

I have this already. I am capturing all the input from Miniquad in a world resource.
As it stands, the input handler is a system that uses a resource that holds all the input info I need (pressed buttons, etc). That system then does the things needed for the input processing.
But at the moment, I hard-code what is accessed for the input system (position, states, etc), and that is very restrictive as I have to define the SystemData struct at compile time. If I want to access arbitrary component data, then this will eventually grow until it (in extreme cases) locks every component, even if most input handling cases only need one of those.
Theoretically I could split everything up and make a handler for each type of input effect that can happen, but that would produce a lot of fragmented code...

If possible, I would like to write callback functions for each "input dependent entity" that lock and get the components they need themselves.

Of course, there is a potential for deadlocking here if I double-lock the resources that are needed from the outside, but I feel like that'd be my user error.