With thunder 1 upgrading to Thunder 3 and Thunder 2 upgrading to Thunder 4, wouldn't it more sense to have Thunder 3 renamed Thunder 2, and Thunder 2/4 renamed Thuderga 1/2.
Also with Bio 2 now gone, Bio upgrades to Bio 3, which can be confusing for new players wondering about where Bio 2 is...
All and all I think the old 1,2,3 naming convention is now more confusing then the -ra,-ga convention.