Spring has sprung out on the ocean!!! (I Like Mr. Kleins signature it has a lot of truth to it!)

Well the way I see it you have only tough days ahead on this problem...

1) Branch Piping can be evaluated separately assuming its Moment of inertia is 25% or so of the header, but note I said it can be evaluated separately, not ignored all together. Evaluation of the branches by visual review is usually easily done using maximum displacements from the header. Stick a linear restraint (X,Y,and Z) on the branch far enough from the header so that you can say that its is isolated from the rest of the run. That way you only have a short segment of each branch to deal with

2) Cut loose the loop restraints.

3) Buy steel to provide linear restraints X,Y,and Z where the main header enters the slip jt platform.

Otherwise ignoring the problems may work in the short run, but eventually fatigue damage will probably show up. When it does the owner may hire an outside consultant who will discover what you have and then say, "The design firm of record knew about this and did nothing about it!"