Copy of gwf in same sim with slight variations?

[wkitlasten]

I would like to load a a specific gwf model from a simulation and make changes and then save it as a new gwf model in the same simulation. I'm hoping there is a shortcut I am missing (something like gwf = gwf.copy(name) would be nice!)... but this is what I have so far:

import copy
import flopy

sim = flopy.mf6.MFSimulation.load()
gwf=sim.get_model()  
gwf2= copy.copy(sim.get_model(gwf.name))
gwf2.modelname = 'gwf2'

So far so good... I have 2 identical gwf models, but I don't know how to change the model name, the external files the packages reference, or add gwf2 to the simulation.

The sim.register_model() method sounds like it does what I want, but the docs warn: "Add a model to the simulation. This is a call-back method made from the package and should not be called directly." Calling register_model did not do what I wanted (no surprise there).

I tried making a new gwf object from scratch:

flopy.mf6.ModflowGwf(sim, modelname=new_name,
                             model_nam_file='{}.nam'.format(new_name),
                             save_flows=True)

But then I need to add packages from gwf to gwf2, which theoretically would be done with something like gwf2.register_package(), but I can't (and shouldn't?) get that to do what I want.

Another option might be to strip out all the package data and create new packages from scratch (e.g. a = gwf.rcha.recharge.array, edit, save as "rch2.txt") then make the new package, but I can't figure out an efficient way to add packages while loop through existing packages, where I somehow need to get the package name p into the package call in place of ***:

for p in [p.package_name for p in m.packagelist]:
    flopy.mf6.ModflowGwf***(gwf2, pname='rch2',
                                 recharge={0: {'filename': 'rch2.txt'}})

Any suggestions are appreciated! I'd hate to come this far and revert to parsing the input files myself.