Support merging map traits?

[kubukoz]

Usecase: Adding traitValidators via apply. Or expanding another map-based trait.

@traitValidators(
    A: { message: "ints not allowed", selector: "integer" }
)
@trait
string T

apply T @traitValidators(
    B: { message: "strings not allowed", selector: "string" }
)

Currently, this emits an error in the apply because trait conflict resolution only merges list/set traits.

Is this something that Smithy could loosen the constraint on?