Re: How big is Starfleet in men and ships?
Though one thing to bear in mind is any recommissioned ships would still need crew even using cadets and the reserve activation clause it might leave ships with diminished crews.
A lot of old ships would already be crewed as they would be in use as patrol / supply / transport support vessels.
Pulling ships out of Mothballs would mean lots of planetside admin and training staff would be pulled into action. You could also probably reassign around 50% of each serving starship crew to mothballed ships - peacetime starships are very overstaffed for war footing.
Soon oh soon the light, Pass within and soothe this endless night, And wait here for you, Our reason to be here...