In my mind, a pi is just another device to manage and another expense. I do not know what phones you have now, but I would use a router phone rather than a pi. The only advantage to a pi is that nobody is likely to unplug it and move it to another cubicle forgetting that other users are dependent on it working. Even better than a router phone is the option of making all the phones router phones -- then there are no dependencies on anything other than the user's own phone.
I'm getting older (65), yet this old dog has learned that a physical phone is rarely better than a soft phone (at least for people who spend most of their day at their desk). I understand that some customers/users just want a physical phone. But as a business person, YOU do not want them to use a physical phone. A physical phone requires more work to setup, it's another point of failure, there is almost no margin (profit), and you have to deal with RMAs (returns). One RMA costs more than you make on the sale of 10 phones. Why would you want to do that? The only reason to put in physical phones is if you WANT the extra billable labor. That's a horrible reason.
Can you pre-prevision a router phone? Sure. Try it. Configure it, and take it home and plug it in. It's an easy thing to test.
Maybe I'm unrealistic, but I think physical phones should be replaced with soft phones in every place where there is a computer/laptop/cell phone/tablet. MAYBE in a manufacturing facility, warehouse, or lobby where there is not a computer available, a physical phone makes sense, but for an office worker, physical phones are an antiquated technology hanging on for just a little longer until all the luddites are all gone.
As an implementer of technology, you want your staff to scale. After all, LABOR is likely your biggest single expense. That means putting in technology that never fails (unless the whole phone system fails). That's why the industry has moved to hosted servers. You set it up and don't really have to worry much about the infrastructure (blades, SANs, power, cooling, wiring, insurance, etc.). Not to mention the expense of all the training and certifications that go with managing that infrastructure. You want to focus on solutions rather than running around hassling with phone issues IMO.
I do not want to sell, implement, or manage physical phones ever again. Back in the day we used to make $400 per phone. Now we make $5 per phone if we are lucky. Screw that. If your customer/user wants a physical phone, they better have a REALLY good reason for it.
