How about:
1 - Tiered Match Play ladder leagues?
You can only challenge a person 3 places above you. If you win you swap places.
If you challenge someone the challenge appears on their profile page and they have 48 hours to play you or they default to a loss.
Players should be allowed 4 weeks of holiday time a year where they can inactivate themselves and freeze their position. Whilst inactivated they don't exist as far as challenges are concerned.
Run it every quarter (winter, spring, summer, autumn) start off each time with an 18 hole single play strokeplay event to determine starting places in ladder. Allow a month of jostling for position with final places determined by average position at end of the month.
Default 45 sec shot timer unless both players agree to longer/shorter time.
2 - Tier-Based Matchplay Knockout Tourneys
Limited entry (64 places). Qualifying 18 hole round (single play) to determine starting positions/seeding.
Matches in each round to be played by a given date, etc etc.
You get the idea.