As an engine builder and someone who has worked on many 1.7 engines including correctly setting the cam timing and also solving many peoples other issues on this site, I am somewhat confused as to why you think using a Vernier pulley would make things easier, please explain your reasoning?
On Standard Cams, Fords would have spent many hours on a dyno testing and trying out different timing settings via Yamaha.
They will have arrived at the best settings and then also then mapped the ECU for the best fuelling compromise i.e economy and Performance.
If you change the cam timing, your fuelling will be out across the rev range , usually then running too rich.
If you want more power consider improving the Gasflow of the Cylinder head, Uprated cams from Kent , Piper or Newman accompanied by a ECU Remap. Something along the lines of what Tickford did when they developed the Racing Puma.
Although Newman lists performance cams for the other Zetec's , they don't list the 1.7. I recommend that you give them a call though.
Here's their current Zetec listing
Here is Kents listing for the 1.7
Providing that your current cam timing is actually correct & everything else is working as it should , the 1.7 is a gem of an engine as is .
It has diesel like low end torque and because of the variable inlet timing, good revability as standard.
What you are proposing .will cost you a lot of money and produce no power or torque gains.