There are a any number of problems with the scenario that you have posted. At this point, you should refuse to seal the project.
1. In designing a project, the architect or professional engineer shall take into account all applicable state and municipal laws and regulations. While the architect or professional engineer may rely on the advice of other professionals (e.g., attorneys, architects, professional engineers, or other qualified persons) as to the intent and meaning of such regulations, once having obtained such advice, the architect or professional engineer shall not knowingly design a project in violation of such laws and regulations.
2. The jurisdiction must have formally adopted the code in order for the code to be accepted practice in the locality.
3. The seal is not, and should not be considered, a certification mark or warranty of correctness. The “seal attests that a qualified engineer prepared the document. It is not a guarantee of accuracy”. Instead, it should be considered a “mark of reliance”, an indication that others can rely on the fact that the opinions, judgments, or designs in the sealed documents were provided by a professional engineer held to high standards of knowledge, skill and ethical conduct.
4. There is no such thing as a "conditional PE stamp"
5. The application of a professional engineer seal shall indicate that the engineer has exercised direct control and personal supervision over the work to which the seal is affixed.
6. Application of the seal and signature indicates acceptance of responsibility by the registrant sealing said documents for all work shown thereon unless clearly indicated in writing on each sheet.
7. Registrants shall undertake assignments only when qualified by education or experience in the specific technical fields of engineering involved. Registrants are not to be restricted to one discipline, rather, as Professional Engineers they are to practice in their fields of competence, provided however, that in the event this Board shall issue registration and/or licenses in a specific area of practice, no person/firm and/or registrant shall practice in that area unless registered to do so by this Board.
8. Registrants shall not affix their signatures or seals to any drawings or documents dealing with subject matter in which they lack competence, nor to any such drawing or document not prepared under their direct control and personal supervision.
9. Some states require that the original (fire sprinkler or system) design shall be by conducted by a NICET Level III Technician, at minimum, who is an
employee of the company contracted to install the perspective system. The design must be reviewed and stamped by a registered professional engineer in accordance with the building official’s handbook.