Good point about the expense impracticality for poorer nations.

On the other hand, is there any meaningful difference between one France and ten? It is a similar progression to Cold War-era nuclear proliferation, the multiplication of warheads to an absurd scale. There are diminishing returns.

If relative power can be quantified as the ratio 1,000,000:1, then adding 100 to the numerator is insignificant while adding 100 to the denominator can meaningfully shift strategy. The latter of course representing the weaker power acquiring a nuclear option. (Essentially, Maoist dialectical principle of qualitative change arising from quantitative change.)

The power balance is so asymmetrical that the actual degree of imbalance does not matter that much. The resistance strategy has to take into account asymmetry as the starting point.