Just wait for 6, 7, 10, confirmations doesn't seems to make sense (mathematically at least), since given enough time any number of computing power will produce the confirmations needed (of course i can use 120 confirmations but no customer want to wait that long), but as I'm kind of new to bitcoins maybe i`m missing something?
So— using time and delaying confirmation when things look weird would be a useful enhancement, but its less important that I think you think it is:
If, say, btcguild goes evil and starts mining a fork which reverses and respends— then yes, given enough time they will mine six blocks. _BUT_ in that same time the rest of the network would have mined 14 and so the chain produced by the rest of the network would be much larger and your client would ignore the chain produced by btcguild.
So the only way this would matter is if they were also able to get enough control of your network connectivity that they could prevent you from hearing about the blocks produced by the rest of the network. The fact that this isn't impossible is why some additional logic would be useful. (Along with peer rotation, explicitly configured trusted peers, etc) But the fact that both significant hashpower and the network attack are required is why it's less of an issue than you might guess.