8 countries rebeled minus Lulusia because it's gone means now we have 7 countries at least. Lulusia has more than 1 million citizens, if we apply the same number to the other countries, then compared to the numbers of Alabasta of 10 million citizens (Alabasta has 400k royal soldiers), with the scale of 1 to 10, they have average 40k soldiers on each island which makes up of around 280k rebeled troops. This number doesn't include the revolutionary army.
I am going to guess it. Take the Marine has 1 million troops (referencing the number of troops we can have today, USA, Russia, China, around 1 million each), and by taking the scale of 170 affiliated nations to 8 rebelled nations, multiply it by 1 million we get 47,059 revolutionary armies.
Sum up 280k rebelled troops and 47k revolutionary armies we get roughly 327k troops.