The problem is that although Sikkim approached the potential of Bhutan in many ways, another traditionalist Buddhist kingdom under an Indian protectorate, it fell short. Critically, Sikkim lacked a clear Buddhist majority population, most inhabitants instead being Hindus with no particular vested interest in the survival of the Buddhist monarchy. That, I would suggest, is why the Bhutanese government ethnically cleansed so many Nepali Hindus when calls for democracy began to be heard in the early 1990s.
You are going to need a very different Sikkim. A government that tries to establish itself as an independent state, not contenting itself with being an Indian protectorate, would be the minimum required.