Variant Modifications was a game mechanic developers planned to add and be worked on after 2.0, but the idea was later scrapped. Variant modifications would have given the tank an upgrade to a different variant/mark. This was purely changing the tank‘s appearance. It is not known whether this was to be done automatically upon a chassis upgrade or purchased separately.
Here is the list of tanks that were to be modified.
Abrams M1A2*Note that the M1A2 Tusk II was able to make it into update V2.2 as a seperate vehicle but the 2nd transition phase was cut out.
Leopard 2*Note that the Leopard 2A7+ variant will be added as a seperate in but the transitional phases are to be cut out.
AMX - 30
AMX - 13