Apologies for the delay answering, had to take care of fiat job for a while. I will brainstorm some ideas:

1. You may have a team competition (US vs World) and then individual (such as Stacker of the year, overall winner in all sports )
2. If you look to different sports, they distribute around the year (soccer August to June, NBA from November to May?, NFL August to January, Cricket all year round, Tennis almost all year round, F1 from March to November). So depending on the running month, we could choose a sport to make picks or provide results.
3. For instance in January, there are some relevant events: NFL play offs and Super Bowl, Australian Open for tennis, last week of phase group of Champions League, and so on. So we have different sports and stackers providing results or picks and obtaining points towards the monthly or yearly tables. We can plan in advance what events we will concentrate (one or two per week). This can be run independently of our existing pools.