Chelsea Pitch Owners main aim is to ensure the club isn't taken advantage of by an owner who wants to develop the land for housing as nearly happened a couple of decades ago.
They're not going to be involved in the financial planning of the new stadium just as they weren't involved in its architectural planning, and nor will they veto any plans for a bigger stadium on the site.
The only question marks around CPO, as I understand it, are whether they'd be willing to sell their freehold to the club. It seems they're not but that's not because they have suspicions about Abramovich or his plans, but because they see themselves as much longer term custodians.
Whatever, this is a situation unique to Chelsea and they're not the only club in the world who've successfully built a new stadium (actually they haven't yet and it keeps getting delayed...diddums). So I don't know why EFC lacking an equivalent is relevent.