I think there's a few preconditions that need to be met before a Sins ladder can be viable. One of them is game length - this should preferably be below 1 hour (~equal to HW2). Many people don't have a patience longer than this, especially if it's a game with relative strangers and there is no guarantee that it's really enjoyable. There's also many people who can't commit daily more than 1 hour anyway. Developing a good format for competitive play is essential if you want to enjoy any, though some casual gamers might find it fun as well.
What would be the requirements for and the options to implement a competitive format? I'm thinking maybe something like this:
- Time limit (1 hour?)
- Some kind of a scoring system to determine winner/draw if the time limit hits
- Extra resources or preresearched technologies
- Readily colonized planets (50% of all colonizable?)
- Prebuilt core fleets
- 1v1, 2v2 or 3v3 locked teams
- Limit on planets, 10 + 5/player
- Limit of colonizable planets (not counting dead asteroids), 6 + 3/player - so in a 2v2 game, the max is 6 + 4*3 = 18 colonizable planets
Please note that this is just a preliminary suggestion, as my experience with Sins Online is still rather limited. Many of these things you can get straight from the map, others would need to be implemented as a mod. You could call the complete system/format Sins Pro if you like 
