I wouldn't mind the use of a virus type. Virus or Vaccine... it doesn't really matter to me. The type doesn't necessarily dictate whether the digimon is good or bad. Guilmon and Impmon come to mind in this again. Well the anime versions. Digimon as far as I can tell behave and learn and grow just like people. Therefore you could use any virus type. 

However, if I say... 
MetalSeadramon will be a one of the core bad guys. please don't have a MetalSeadramon. 
If I say Belphemon... Don't use Belphemon. 
Etc. etc. 
Understood?