Having had a think about this, there might be a quick fix, if it is doable?
Rather than worrying about all the league back end,
If the the club owner went to the add fixture screen as below
And the league & radio buttons was taken off the form.
The user could simply add the two team names as he currently can in that screenshot above.
To make it a bit more fancy could you add an option to select if it is a friendly or a league fixture
And if it is a league fixture could the club owner type in the name of the league themselves same as they do for the team names?
I think that would work quite well and be sufficient for club owners to have a record of their upcoming fixtures and played fixtures
What do you think?