What about some advanced scripting foo?

Ask players to sign up, specifying their region (which is then used to sort people into groups by region, or half/half).
Then ask players to mark a certain minimum number of hours during "reasonable" times in their timezone (e.g. 5pm to 10pm during weekdays, 12pm to 10pm during weekends, something like that) in a scheduler.
Then players can challenge other players on the website simply by selecting a free slot in their opponent's schedule (in addition to spontaneous chat challenges).
Combine this with email notifications and mechanisms to aid rescheduling if needed, and there is practical no limit to how much you can help matters to move along smoothly.
Creating the software for this is not going to be trivial, but why not give it a try? It can be set up as an open source project, and there is no rush to get it done anytime soon. The worst that can happen is that it never gets finished.
For what it's worth, given that I am thinking about joining, but the above mentioned issues do worry me a little, I do expect that I would have enough motivation to make some time to work on this.