Failed to ParentScope a variable array

[GRCROWN]

I want to share parameter arrays and variable arrays between root system and child systems. ParentScope works on parameters and variables, but I don't know how to ParentScope a variable array or a parameter array. It seems ParentScope failed on a variable array.
MWE:

using ModelingToolkit
using ModelingToolkit: ParentScope

function a(; name)
    @parameters t
    @variables x(t)[1:2], xx(t)[1:2]

    D = Differential(t)
    eq = [D(xx[1]) ~ ParentScope(x[1]), D(xx[2]) ~ ParentScope(x[2])]
    return ODESystem(eq; name)
end

function main(; name)
    @parameters t
    @variables x(t)[1:2]
    D = Differential(t)

    @named s1 = a()
    eqs = [D(x[1]) ~ 1, D(x[2]) ~ 1]
    sys = compose(ODESystem(eqs; name), s1)
    return sys
end

@named sys = main()
structural_simplify(sys)

And I got:

ERROR: ExtraVariablesSystemException: The system is unbalanced. There are 6 highest order derivative variables and 4 equations.
More variables than equations, here are the potential extra variable(s):
 (x(t))[1]
 (x(t))[2]
 (s1₊xx(t))[1]
 (s1₊xx(t))[2]
 (s1₊x(t))[1]
 (s1₊x(t))[2]

Root system and subsystem s1 have different x[1] and x[2], and I expect (x(t))[1] (x(t))[2] (s1₊xx(t))[1] (s1₊xx(t))[2] only.
I also tried x=ParentScope.(x), x1=ParentScope(x[1]) and some other stuff, and all these failed. Could anyone show me the right way to do this? Or it's just unworkable temporarily?

[AayushSabharwal]

This works now