Impacts of "professional advisors" for undergraduates
I've been to schools with both systems, so I'll give my perspective as a student:

The Third pro you list (a professional advisor being more specialized) is HUGE. Students get very frustrated when their advisor doesn't have the answers that they want, and in my experience, most of the questions that students ask are for administrative stuff, like, "How do I sign up for classes" or "Can I skip this prerequisite?" that a qualified advisor would be able to easily take off of your plate, and would probably be able to handle more quickly, which would improve the student experience.

Addressing the cons: You should not be concerned about an advisor steering students away from your program. That would be horribly unprofessional for them to do, so that would be something I'd wait for it to actually happen before addressing it. As for the fact that they might not be as qualified to deal with certain problems, it would just be a common part of their job to come and find information that they aren't qualified to give. The lack of a long-term faculty relationship is a real concern though.

Additional thoughts:
Providing a single point of contact for students is a very valuable thing indeed. A person whose sole job it is to listen to students and address their problems has always been very helpful for me, because I never felt like I was bothering them when I went to ask them a question, which is how I felt any time I was talking to my normal faculty advisor. It also makes it easy to know who to go to with a question early on. You don't have to remember your specific advisor, you can ask anyone and everyone will know who the advisor is, and be able to point you to them.