Oh, the joys of leapfrogging hehehe.
That aside, here are some concerns:
Length of Season:
With summer approaching, we might not want to have a long season. In a ladder, the games pretty much take care of themselves so that shouldn't be much of an issue. As much as I've had a love-hate with the current D8/D6 league, it's just too drawn out. After we've done our...8 or 10 week season we'll have another two to three weeks of playoffs? More than that if we need to do a home and home for each playoff series? So that's around 15-16 weeks...that's a crazy amount of time to commit to PvP with patios opening, BBQs getting dusted off and whatnot.
Prizes:
Of course, you need a reason to play. We're not going to get prizes from PvPEC if they're not involved, but I'm sure we could gather enough inf/stuff to make it worthwhile for people if they wanted them. I remember the old ladder gave titles at the end/start of every month to the top team? We won't get the titles but maybe an inf purse or something, or just Merit rolls

shouldn't be too hard to get.
Structure:
So if we do a ladder, we'll need to have a ranking tourney. Easy enough. Then you'll need to do a challenge system. The old ladder let you challenge two rungs above and below and worked fairly well, though it was pretty funny when OS challenged the entire ladder when things died down.
We probably want to avoid having teams challenging each other over and over only to leapfrog endlessly. Perhaps setting a delay on a challenge to another team would be nice.
Line-ups:
Going to need some policy on having teams loaded in on time and present as well has a "once you're in, you're in" to prevent DCs and replacements by something else because your opponent brought something. Additionally, there should be some discussion on whether certain ATs/Powersets should be limited...
External factors:
Would be nice to have a break after the current D8 thing is done, it's gone on a long time.
Power changes or any PvP changes coming with Going Rogue might impact line-ups.