The arguement they could be making is that they took a drug expecting it to be cocaine... It is different than taking something which has a list of known ingredients or a known producer who could be questioned. They could in fact argue that someone else has "tampered with" the cocaine they bought by cutting in with Clen.
That is not a moral excuse... But there is potential that it could be a valid legal one... And given the AFLs soft illicit drug policy that may be their best bet to get a reduced sentence.
Personally i want them to get done. I think it will be a strong lesson to all footballers and to them as individuals. For the club, yes it would be good to get them off somehow but what message would that be sending to them and others?
There's no way ASADA or anyone else would accept that excuse. As you say, it's different from taking something with a known producer and reliable list of ingredients. In fact, that would be the line of questions:
1) You attended briefings where they explained strict liability, yes?
2) Did the cocaine you took meet any of the standards necessary for you to have satisfied that responsibility?
3) For instance, did you know exactly what was in it?
4) Did you know who prepared and where?
5) Given you should have had doubts about its fit with the WADA code, did you consult with ASADA or your team doctor before taking it?
6) You're not very smart, are you?
ASADA and WADA will hold to the position that there is no foolproof way of knowing exactly what is in any illicit drugs you take, and therefore you mustn't take them due to the risk of copping some PEDs.