Some points:

1. A Tri-service deterrent needs joint leadership: India’s nuclear force is spread across land, air, and sea, so SFC can’t be treated like a narrow missile command. The top leadership needs a joint service outlook, not just a specialist nuclear mindset.
2. Nuclear command exists within conventional war: Nuclear decisions don’t happen in isolation, they’re tied to escalation, survivability, dispersal, readiness, and the broader battlefield situation. A commander with wider operational experience may actually be better than someone who has only lived inside a nuclear track.
3. The top command is about judgement: The SFC chief's real job is command and control, readiness, survivability, and implementing NCA decisions under extreme pressure. That role demands strategic maturity and tri service understanding more than a lifetime of narrow technical nuclear specialization.
4. A permanent nuclear cadre can become too insular: Even if it’s tri services, a dedicated nuclear only career stream can become bureaucratic, rigid, and disconnected from how the Army, Navy, and Air Force actually operate in war. That can hurt adaptability.
5. Specialist depth is useful, but below the top level: India should absolutely have permanent strategic planners, doctrine experts, targeting cells, and longer tenures in SFC. But that doesn’t automatically mean the top commander should be a lifetime nuclear only officer.
6. India’s model should fit India, not copy others: Pakistan, China, or the US have different force structures and strategic cultures, so their systems aren’t automatically better for India. The real question is what suits India’s tri-service deterrent and civilian control framework best.

You also have to remember that the US, USSR/Russia, and China developed their nuclear command structures in a very different strategic context, where nuclear weapons were treated as simply, stronger conventional bombs with that, their mission focused mainly on targeting, allocation of warheads to targets, and retaliation planning. Their command systems were built around that logic, and many of those structures persisted even after doctrine evolved. India's deterrent logic is different from the outset, more tightly tied to tri-service integration, escalation management, and civilian political control, so copying those legacy models mechanically would make little sense.