Form Builder: Create Other Field for Select/Custom Type

Hey so I need to add support for an "other" field that will allow a custom text box to appear on the frontend, the way the data is sent is an array of submissionData

{
  "field": string,
  "value": string,
  "id"?: string,
}

If i'm using a Select type and want to allow the extra field how should I go about submitting the text field data and adding the other field to the inbuilt type for it?

I've also got a custom type called "multi-choice" which basically identical to select, but just different blockType so it's easier to differentiate the type of form element to show on frontend and also Select doesn't support multi-select options it seems.

I've added an Other checkbox to say if the form creator wants to allow the custom field, but I'm unsure how to submit it, current idea would be to send it in the value key like

{
  "field": "multi-choice",
  "value": "other:Custom Text Goes Here",
}

correct me if i'm wrong but this would fail validation as the value doesn't match an option.

so would I just extend the submission data type or is there another way that would be recommended

{
  "field": "multi-choice",
  "value": "other",
  "data": "Custom Text Goes Here"
}

your prob best person to ask about this

next solution I currently have is to add a new field on the form that has "nameOfField-other" for accepting the other fields so it doesnt modify the returned data, and would just be an optional field returned. this gets added via a field hook for the multi-choice field, but unsure how I could add the same to the select field outside a collection hook?