Provide a way to force the universal media player to control a specific child media player

According to the docs: “The Universal Media Player will primarily imitate one of its children . The Universal Media Player will control the first child on the list that is active (not idle/off).”

In some cases I would like to be able to choose which of the children should be controlled by the universal media player, even if that specific child is not the first one in the list that is not active.

For example, in my setup I have a universal media player with children, which are both Spotify streams:

  - platform: universal
    name: Music Player Living
    children:
      - media_player.spotify_jimbo
      - media_player.spotify_lola

Right now this setup will always have the universal media player controlling the first child when it is active, even when I am listening to Spotify in my car while my wife is listening to her Spotify stream at home. In that case I would like to be able to force the universal media player to take control of the second child, so my wife can control her Spotify stream through the awesome HA interface like she’s used to.

I noticed the universal media player has an attribute called active_child:, so providing a way to update this (e.g. through a service call media_player.set_active_child or something similar) would be really useful for my setup.
Currently I have a workaround, using the state-switch card in lovelace to display the correct media player entity, but it’s a pain every time I have to update the card configuration, since everything has to be changed at least twice (per card).

Thank you for considering this feature!