I hold a NJ master electrical license, still hold a business permit and have business insurance. I no longer operate my own contracting company. I currently work full time as a building operations director. I have an opportunity to work a deal with an existing reputable mechanical contracting company to attach my license to their business. I would be part of their payroll but will not be part of their day to day operations. Full details of this potential agreement have not been finalized.
The first thing you should understand is that whether you will be eventually found personally liable is a distinct question of whether or not you can assume that you will not get sued. Your license as an electrican provides a potential utility to contractors who do not have enough electrical work to justify the full-time employment of a licensed electrician.
Does this mechanical contractor perform residential improvements? If so, having your stamp on the electrical permit could expose you to personal liability under the dreaded NJ Consumer Fraud Act (the "CFA") - the bane of the NJ residential contractor. Violators of the CFA are liable for treble (triple) damages on any ascertainable losses by the consumer PLUS the homeowner's attorney's fees. Because the CFA is remedial and was enacted to protect consumers any person who makes an improper commercial representation is potentially liable.
If the mechanical contractor does residential work, you should probably negotiate some type of hold harmless clause into your agreement with them. Even if the mechanical contractor focuses on commercial projects, securing some type of indemnification would be appropriate if your license is being used or employed in a manner which you have no ability to control the associated work.