My opinion is that you wouldn't gain anything by parking nukes at ISS. A better place might be Sun/Earth LaGrange points.

Also, I wonder how suitable SRBs are. Can they take longterm exposure to vacuum (how volatile are the components in vacuum?)? Likewise (since they don't throttle well) they would require finding a trajectory that uses exactly one SRB-worth of thrust at the beginning of the mission.

As for guarantees of *breakthrough* science at ISS: there are no guarantees to be had. No one can give you a guarantee like that about any scientific research (eg: will someone guarantee that the CERN upgrade will find the Higgs Boson?).

I'll give you my personal guarantee (worth absolutely nothing!) that:

1) providing that the crew-shortage problem is solved, and the rest of the science and power and heat componants are installed, that
2) a lot of science will be done, and
3) a lot of that science will have the quality: results-very-hard-or-impossible-to-get-from-earth.