I tend to agree with most of what you have wrote. However, the Bill's have made two concerned attempts to improve their oline, so heralding the "stop-gap/another team's castoff" line is a bit misguided. The first of these of course were the big FA signings of Dockery and Walker, the second came with the drafting of Wood and Levitre. The 1st was an epic fail, the jury on the second is still out.
I would think we'll have a much better idea of how Bell and Wood are after a year of strength training coming off the injury. Levitre is solid, and actually was our best lineman last year.
Right tackle is very weak. You're right, and now with Wood probably being shifted to center, it leaves the right side of our line in a state of flux. I agree Urbik, Wrotto, Pears, Hangartner, and Wang are not the solution. Solid depth perhaps, but not the type of starters that can allow an offense to excel.