Why “not simply a relate field”, if a relate field matches your description of what you’re trying to achieve? (no subpanel, just a field in the edit view).
That is possible but it won’t be easy. It subverts the way SuiteCRM is designed; you would have to save a different record when saving a Contact.
You can override the Contact’s Edit view class in PHP but get ready to face some challenges…
You might find some example online if you’re lucky (probably for some old SugarCRM CE), try searching for adding related field in edit view or something. Good luck. If you get it to work, please come back here and share how you did it.