Nice as it might be I feel there's just too few airframes to start extending the role to armed tasks. As it is I'm concerned the ISR planned for the new 'J' fleet might morph into the touted 'complimentary capability' for the P8... there's just too few J's to also take on a sustained 'lite MPA' role. Also there is no obvious policy for an armed role mentioned in the DCP.
Arguably it could happen under the radar with Oz wanting to maybe move some surplus pods and if it's then possible to arm them with a smaller (ie: cheaper and less contentious) weapon fairly easily... something like a mini-gun, then it could be an outside chance. However gut-feel is no, and that 5 'J's' isn't enough longer term even just for transport tasks.
I can see both the value in, as well as few reasons for the ability to mount/carry podded ISR kit.
One of the first would be to make any RNZAF C-130J engaged in aeronautical SAR both more valuable and more effective. Carrying out a volume search, especially at a distance for something like a missing vessel or missing/ditched aircraft (airliner in particular) would require as many 'eyes' as can be gotten into the area. Having the -J's able to be kitted out with something more effective than Mk I eyeballs would help. The -J's could then also potentially airdrop emergency stores/supplies should survivors be detected as well.
Another potential scenario where podded ISR kit would be useful was if a -J was deployed away from NZ in support of NZDF operations in an area where eyes in the sky would be useful in monitoring a situation, but the conditions or distance would not justify deploying a P-8, but an airlifter would be worthwhile.
Arming the -J's I do not think with be VfM, due to both the costs, but also the range of scenarios where arming a large, slow airlifter would be both useful and not exposed to undue risk.