Your question is an outstanding one, and as you have already retained and spoken with a patent attorney, and I am NOT a patent attorney, I can only share some thoughts.
There are some people who like to file for and get a patent primarily to put up on the wall (like a diploma) so that they can proudly say that they have been issued a patent, or who can use the fact that they were granted a patent to butress their resume, use it to land a job, substantiate that they are indeed an inventor, regardless of the real commercial potential of their patent.
I do not know how many of the 6+ million or so patents that have been already issued were sought expressly for what is essentially "ego".
I do know that most of the inventors who had thought that their invention would make them rich, never saw a dime of revenue. They retained counsel, filed a patent application, paid the expenses involved and only then found that their invention had no commercial application, or that at least THEY could never successfully exploit the invention. (Are there some figures that say fewer than 10 percent of the patents issued had ever been successfully commercially exploited?) For those folks, their patent, in essence, is another diploma to hang on the wall.
If your improvement is indeed novel and useful and thus patentable, I would think (as a non-patent lawyer) that you might well be able to get a patent issued. However, to the extent that your improvement required or relies on the technology covered by the original patent to be operational, for the life of that original patent you would not be able to independently manufacture the "improved widget".
That does not mean you might not license the improvement to the holder of the original patent, which might create some revenue for you. Or you might wait until the old patent expires and then use it and the new patent you get to reissue the product.
As for the allegedly over-broad scope of the existing patent, that may be the killer. Mounting a patent challange to knock it down can be an expensive process.
To the extent that your improvement is covered by the overbroad patent, that suggests your invention would not be regarded by the Patent Office as novel and thus not be patentable, and I think would block your getting a new one. You lawyer may have been doing you a service. On the other hand he may be toally wrong and if you feel strongly about it, you should seek a second patent lawyer's opinion!
[Edited by ALawyer on 01-23-2001 at 02:00 PM]
This is intended as general information only, NOT legal advice. You are not my client and I have no obligation of any kind to you. To retain a lawyer I suggest you go to www.AttorneyPages.com.