I think the ranks update is nice. And I think it's good that players who will automatically be 'Legend' will get some crystals when the update is introduced. But I don't think it is fair that players with different levels of 'Legend' will get the same amount of crystals.
Example:
If I have 2 siblings who both play Tanki (a lot), and the older one started before the younger, so has around 2.8 million exp, and the younger one has 1.6 million. I guess that makes the older one 'Legend 7', and the younger one just 'Legend'. Yet when the new rank is introduced, they will both get 40k crystals.
You said that one of the points of the update is for generalissimos to compare what level they are. Well, when my younger sibling ranks up to 'Legend 7', they will have recieved 280k compared to my older sibling recieving 40k now for being 'Legend 7'. So my younger sibling will be 240k better off crystal-wise at 'Legend 7', than the older sibling. So they can improve their garage more, get more supplies, whatever, and so be 'better' at the 'Legend 7' rank than my older sibling was.
When the older sibling bought their m3s, they had to buy the previous modifications (m0, m1 and m2) to get the m3s. And then the update was introduced so that you could buy the m3 without buying the other modifications, so my younger sibling got to buy their m3s at essentially half the price of what my older sibling paid. Not to mention the fact that my younger sibling also benefitted from having the garage discount when you own a certain amount of hulls/turrets, and also having daily missions, and the daily mission chains, to give them extra crystals for a greater percentage of the time they've been on Tanki compared to my older sibling.
They both play similarly, and make similar garage choices, and yet the younger one already has a garage much much better than the older one did at the same rank. So recently-joined players are getting an advantage over players who joined slightly less recently.
Even if you don't want to give players with higher 'Legend' levels the full amount of crystals (ie 40k x the 'Legend' number), at least you could give them more than what you're giving players with lower 'Legend' levels. To make it more fair.