I could have sworn that this topic was about Tigers...
Back on Topic, I don't see the harm in making Tigers a call-in unit, sorta like the Panther Battle Group,
1) Do something... build every building or whatever
2) Pay 500MP, 100Muni, 80Fuel, or whatever
3) 900MP, call-in, up to two tigers on the field,
PS, If your opponent has 2 tigers on the field, that means they invested 1800Mp, and what have you been doing all this time?