Damage said:
Nope, the M551 is and Armored Recon Vehicle. Just cause you have tracks, guns, and armor doesn't make you a tank. Look at the Bradley... us cav scouts hate being called 'tankers.'
Well, having tracks, guns and armor pretty much fits the basic definition of tank. If you look hard enough into history, you'll find out that even having large-caliber gun is not necessary (many early tanks were armed with MGs only) and troop-carrying capacity does not stop a vehicle from being a tank (e.g. some WWI tanks and Merkava ;-) ).
The fact that modern armies developed a lot of other names for tanks, based on the intended mission of said vehicle (including Main Battle Tank - what most people consider a "tank" right now), but the basic tank definition has not changed - and no amount of intra-service rivalry will change that...
BTW - you call M551 an "Armored Recon Vehicle". Its armament, armor and mobility is slightly inferior to XM8 ("Armored Gun System") which is slightly inferior to TAM (Tanque Argentino Mediano - Argentinian Medium Tank)... At which moment you stop hiding behind mission-based names to call vehicle a tank ? ;-)
As for the scenario-based approach, I agree. If you want airborne insertion, you need a scenario, which (among other things) will limit the availability of armor to the airborne force. Don't forget to include rules that will allow defenders on the ground to slaughter the airborne while they are still in the air, however - drops into hot LZ tend to end this way...