WHAT'S THE DEAL WITH THE MOD LIMITS? My thoughts...
Here's my musing: As I like to say (didn't invent the phrase, but pretty close), "on the Internet, if you aren't paying for the product, you ARE the product." This is especially true for, well, anything Google does. (I use a ton of their stuff, so am not complaining, but it's worth being eyes-open about.)
What does this mean for Ingress? Well, they aren't providing the game out of the goodness of their hearts. They've come up with a way to get all of us to walk outside, to stand around locations of their choosing (or better, to slowly walk around those locations and pause on top of geographically-dispersed resonators). We do this with GPS turned on, at minimum the cell-data radio, and usually wifi as well. This provides an incredible source of data for Google (remember, they eat petabytes of data for lunch). They might be using it to provide data for future walking maps/directions, to refine location services, to study radio effects as you move in and out of reflections, or even to classify how connectivity for each type of Android phone (or radio chipset, or Android version, or whatever) behaves in the wild.
The point is that *it isn't about the game*. They have done an incredible job providing an insanely well-thought-out, complex-backstory, fun, team-building, exercise-inducing system. But the game isn't there for us, it's there for their data collection purposes.
So: in that light, per-level resonator limits (requiring more people to visit the same portal together or separately to get a high-level portal) makes sense. As does not bothering with levels past a point where at least 8 different people have to each go to the same place. Making portals easy to destroy and requiring more teamwork to rebuild makes sense. And to the point of this discussion, mandating only one mod/player, well, that gets more people to have to visit the portal, especially if Google is not totally satisfied with the amount/mix of people visiting to attack. Makes sense.
In my humble opinion, those raging at the rule change or trying to deduce why (in game terms) Google would do this are missing the point. We aren't paying for the product, so we ARE the product. As such, Google is free to manipulate us however is most useful for their purposes.
Again, this isn't nefarious -- we're free not to play, and if it weren't fun enough we'd all drop out. But it explains many of the rule changes better than any other explanations I've heard.
I have no special knowledge nor connections with Niantic or whatever. I could be completely wrong. I'm just making my inferences as a high-tech geek and especially what I would do if I had Google's business model and resources.
The rule changes don't have to make sense. They just have to not be so horrible that too many people ragequit.