Affiliate Conversion Tracking problem, Please help

Hi guys

I read/heard there're many ways affiliates can do conversion tracking for PPC campaign in order to optimize the keywords, but what's the best way? Some of the method i know is,

1. Google Adword Conversion Tracking - it seems really good, however, I think to do google conversion tracking ,we need a thank you page, right? But usually on our affiliate landing pages, our call to action button directs visitors to the merchant site. Then How can we make a thank you page? The only way i can think of is redirect visitors from the "thank you" page to affiliate tracking URL just for the sake of track that conversion? But would google find out and allow such endevour?

2. SID tracking - I'm with CJ. However, to do SID tracking with thousands of keywords, we need to ask merchants to put a code on their page i think? Correct me if i'm wrong. But usually merchants don't give about small fishes, (imagine if every affiliates ask for that)

3. Xconversions - I heard this software from Jeremy Palmer as well as Amit Methr (super affiliates). Is this software a good tool? It's asking details like FTP username, passwords, etc etc and the CTO in my company is worried about this. I don't know how to convince him to not worry (actually I don't even know myself if giving these details to them are good).

As you can see, I'm bit stuck at the conversion traffic phase (which is stupid i guess).. But I know I really need conversion tracking in order to optimize my PPC campaign ..

Anyone can give some advice please

many thx