telcogirl,
Either of the two Durafon solutions I stated earlier would work for you. What you need to figure out is how many phones that you want to work independent of one another. Basically you would need an analog port per Durafon cordless phone you would need to work. Then you would need to find the Durafon solution that supports that many individual analog ports.
Then you put an Analog port to the Line port of the Durafon base and then program the Durafon base to have any calls coming into that Line port to only ring one particular Durafon associated with it. The most we have done this way was 12 Durafons which required 3 of the 4-line base systems or kits. This can get really expensive really fast, but it is the best solution for those types of environments.
I am not sure why your technicians would have a problem directing calls to ring any of the individual Durafon extensions, but then again they may not have programmed the Durafon base to have 1 line go to 1 extension before either.
I don't know how they solved the problem with the Norstar, but the 5000 does have the ability to use an ATA as well so you could just replicate their solution.
Thanks,
TE