slide-rs/specs

Hello there, I'm coming back to creating a text-based game using Specs and I can't figure out a good way to handle input. In my mind, a command (like attack) is composed of selectors (CreatureSelector and WeaponSelector in this case) that are responsible for associating a slice of input to something in the world. Those selectors must run in a given order defined by each command, and they all have very different needs in terms of storage reading. The most practical way I've found is to create custom system traits and my own dispatcher like so:

pub trait Command<'a> {
    type Data: SystemData<'a>;
    fn get_selectors(&self) -> &[Box<dyn ExecuteSelector>];
    fn run(&self, args: Vec<Selectable>, game: &Game, data: Self::Data) -> CommandResult;
    fn setup(&self, world: &mut World);
}
pub trait ExecuteCommand<'a> {
    fn get_selectors(&self) -> &[Box<Selector>];
    fn run(&self, args: Vec<Selectable>, game: &Game, world: &'a World) -> CommandResult;
    fn setup(&self, world: &mut World);
}
impl<'a, T> ExecuteCommand<'a> for T
    where T: Command<'a>
{ ... }
pub trait Selector<'a> {
    type Data: SystemData<'a>;
    fn parse(&self, input: &str, game: &Game, data: Self::Data) -> ParsingResult<(usize, Selectable)>;
    fn setup(&self, res: &mut World);
}
pub trait ExecuteSelector<'a> { ... }
impl<'a, T> ExecuteSelector<'a> for T
    where T: Selector<'a>
{ ... }
pub struct CommandDispatcher<'a> {
    commands: Vec<Box<dyn ExecuteCommand<'a>>>
}
impl<'a> CommandDispatcher<'a> {
    pub fn dispatch(&self, input: &str, game: &Game<'a>, world: &'a mut World) -> Result<(), DispatchingError> {
        // Find which command to trigger based on the start of the input and strip the matching part.
        // For each command's selector, run it and remove the matching part of the input. Add the results to a list of arguments.
        // Run the command and pass it the list of arguments.
    }
}

Of course this is a simplified version. But I think that this defeats the purpose of an ECS...
Does anyone have an idea on how to put it differently? Many thanks in advance!