Suggestion

Let's say cats cost $10 a unit (logical since you get 10 prestige for killing one), cavs at $4/unit, archers at 2, and inf at 1.
To buy a force of 10,000 cats (a big number for low levels) would cost $100,000. Seeing as gems can cost that much and you need one to upgrade to level 7, with some dedicated saving, someone could pull that off at lvl7. On a newer server, that player could cause some serious damage to his peers. AND, since he did not train those troops himself, he did not get the 100,000 prestige that entails, and so the prestige rating coefficent will not affect him. He will be using a level 14+ class army but not getting the same penalties a level 14+ player would get.

How about we go bigger. I want to buy a force of 100,000 cats. At the rates I quoted above, that would set me back $1,000,000. A large amount, but not impossibly so, especially if your techs are maxed and you have nothing else to use the money on. There are probably 10 (liberal estimate) non-hackers on even s101 who would have that army. Ten players. Out of probably 3,000 active ones. I could cause some serious damage with an army of that size, or, if I waited longer, twice that size. And the beauty of it is, I can just sell them back at the end of the day, assuming once in market troops don't consume cropflow. (If they did, the above situation would be more unlikely, but most top players could save up enough to go on a mad rampage for a few days).

At any rate, the need to buy resources to mass train troops would become obsolete, and there would be no need to actually spend time training them chunk by chunk yourself.

I completely agree. Also, this brings up a good point - the market could be used as it is with resources, as a storage unit. One could put in troops for high prices, which would be the same as sending them to an oasis only they would not need any crop.

Buying and selling troops is just a bad idea anyway.