Your business scenario is a fine example of the People - Process - System (technology) interface. Mark and Craig both offer some interesting thoughts. Here are some more that may lead to a workaround:
Create a "logical" Branch/Plant for Research & Development or Engineering, or test, or new product development. Call the new B/P whatever you want, and use it for new product "front end" stuff. Do not create B/P records in the "normal" B/Ps for the new item until it is ready for release.
Control the new item's "status" in the R&D B/P perhaps by some new Lot staus codes that you will define. The status codes can be updated as the item progresses through its life cycle until it is ready for "release". That whole new product development and introduction cycle can be predefined, montored, and controlled by use of the ECO routing process, including creation of regular B/P records after final approval.
This approach may require more discipline than most companies are willing to endure.
In my experience, some clients have attempted to control new product development via one or another 'third party" engineering/design software package. Interfacing that third pary data to JDE has always been a challenge.
A related issue to address involves the questions of who (functionally, not necessarily by employee name) owns and controls the Item master data set for the new item, when does that 'ownership" change, and to whom does it transfer?
Phrased differently, who has access to enter/change Item Master data, and what is the source that authorizes the specific data entry/change?
Clearly, whatever system solution you opt for, you will have to address the people (training & discipline) and process (procedural) requirements.
Good luck.