Is it possible to add "planets" to the gearbox of a Trent 1000?
The fundamental question you seem to be asking is whether adding more planets to a planetary gear improves the load carrying capability of the gearbox.  The answer to that question is yes... to a point.  

Take a look at a picture of the PW geared turbofan gearbox.  You'll note that there are five planets in there, and they are packed in pretty tightly.  There's really no room to add any more.  Although adding more planets would distribute the load such that each planet takes less load, it's impossible in this configuration because there is no space.  Let's say that you really really wanted to make it six planets instead of five. The only way to make enough room would be make the planets smaller. As you make the planets smaller, then either the ring gear has to get smaller too, or the sun gear has to get larger.  Either way, that is going to change the gear ratio (see formulas here). Specifically, the gear ratio is going to get closer to 1, which means the gearbox no longer does the job it was intended to do (namely reduce speed and increase torque).  

So you can't have your cake and eat it too.  If you want 16 planets in a planetary gear, you can do it, but the gear ratio will be something like 1.02:1 which is not useful.  You might as well forget the gearbox and just do direct drive at that point.  If you need a decently high reduction ratio like 2:1, you can do it, but you will be limited on the number of planets that you can fit in.