Reverse engineering takes longer than a product cycle

Although lawyers are not that stupid, signers of said NDAs should not be stupid and passive as well - for one I was always adding to the NDA being signed for the purpose of getting access to the documentation for a device - "It is though fully understood by the Parties that nothing in this Agreement shall be used to prevent <our side> from developing and releasing the source code and software design documentation for Linux Kernel device driver module for the devices, covered by this Agreement, under the terms of GNU General Public License, v2, see Appendix G) made integral part of this Agreement"

And if THEY refuse to sign it like that - so be it. Look for another chip vendor. There are enough chips designed to find one that meets your requirements, in both technological and legal areas.