I too eschew the word shall where the imperative verb is more direct, but also find that in a few cases it is the still clearest way to indicate that the contractor is required to do something. The CSI Manual of Practice, which should be definitive for usage in the construction industry (notwithstanding whatever Blacks Law Dictionary may say), says the following (p. FF/170.2, 1992 edition):
Shall and Will: Shall is used as an imperative in reference to the work required to be done by a contractor. Will is optional and is used in connection with acts and actions required of the owner or the architect engineer (A/E). The words must and is to are not recommended.
John, I suggest that the point should be made as diplomatically as possible that the requested change is exactly the opposite of accepted industry usage and official industry definitions and recommendations, and is likely to lead to confusion and unintended interpretation. If forced to comply despite this, document the point in a written CYA communication to the agency and keep a copy in a secure location.
Recently I read that in the U.S., shall (but not will) conveys an imperative sense (a command), whereas in Britain, it is just the opposite: in the U. K., will is the imperative, not shall. Perhaps the attorney has been unduly influenced by legitimate-but-British authorities, not realizing this fundamental transatlantic difference.
Shall and will yields about 8,650 hits on Google, some of which are mind-boggling discussions that touch on this very issue, among others. The two words have quite a history. As will be seen below, the wrong understanding could be a life-or-death matter. For an exhaustive treatment from Fowlers The Kings English (1908), go to SHALL AND WILL - Collection at Bartleby.com
For a striking example of the inherent misunderstanding with which this is fraught, go to http://202.186.86.35/services/printerfriendly.asp?file=/2004/8/11/features/8537335.asp&sec=features, where you will find the following (in which will is evidently used in the older sense expressing resolute determination or force of will about ones own action, and shall is an imperative, albeit in this instance a negative one):
THERE is an ancient story, which all students of English are forced to hear. It goes like this: a swimmer gets into difficulties. He cries out: I will be drowned, and no one shall save me! All who hear him turn away and leave the wretched fellow to his fate. That is because they believe he means it, and that he intends to drown. These tough-minded grammarians take it that the unfortunate swimmer is intent on suicide, and that it is none of their business.