Querying select-field options from multiple structure-fields + possibility to manually enter option?

Is it possible to query select-field options from multiple structure fields and also offer the user to manually enter an option if none of the ones queried fits?

A specific example

Let’s say I’m working on the website of a company. The company has many employees, some of which belong to certain teams. An employee can belong to multiple teams at once.

The website should include a page on which a list of all teams is displayed. Let’s call this page »All Teams«.

Each item in the list on »All Teams« should include a (nested) list of the employees belonging to the team.

In the CMS, the user can create the teams for this list by creating/adding them to a structure-field.
This structure-field contains a nested structure-field in which the members of the team can be selected.
In this nested structure-field, the user should be able to select the members of a team from a select-field (rather than typing them in manually) OR type in the employee’s name manually if it is not included in the field’s options.

Question #1: Is it possible to create a field that accomplishes these two things at once (selecting an option or entering a manual option if none of the presented options fit the user’s need)?

Question #2: Is it possible to query the options of a select-field from multiple structure-fields?

To explain Question #2: Given the described example, because an employee can belong to multiple teams, ideally the select-field to select the members of a (newly created team) should query all team-members previously entered/added to other teams. So the field’s query would have to fetch all team-members of all other teams.

I hope this makes sense, please correct me or ask if there are mistakes in my logic.

Finally, I know another option to accomplish something similar would be to create a separate structure-field in which all employees are entered/stored and then query the entries of this field as the options of the select-field with which team-members are selected:

  type: structure
  label: Employees
      type: text
      lable: Name of employee

  type: structure
  label: Teams
      type: select
      options: query
        fetch: page.employees.toStructure
        text: "{{ structureItem.name }}"
        value: "{{ structureItem.name }}"

But, given that Question #1 can be answered with yes, it would be much nicer if the options were queried dynamically from the teams which have already been created.

Question 1: A select or multiselect field does not provide the option to add something manually. The only way to achieve that with Kirby’s default fields would be a tags field.

Question 2: Yes, that would be possible via a custom method (page method or model) that returns an array of options from all structure fields).

A multiselect inside the structure would probably make more sense than multiple single selects?