I am seriously concerned about the value of CISSP would bring to your future career, since you don't have the majority of domain exposures, seems, and the amount of effort you will have to invest. Simply put, I don't see the favorable ROI in your case.
As a first step, you might want to consider to join several security organizations, such as ISC2, ISACA, SANS, to see if any knowledge/certification that might help you in your future career growth. Another option is to see if you can obtain some government security clearance, being an RF engineer.
Getting an MS degree online in IT related field with specialized in security may be your other option, as a degree can certainly enhance your marketing value.
Best of luck,
Next to the technical skills I would like to recommend also not to forget to improve your soft skills. If it is suitable for you to acquire T-shaped skills can offer much wider view to the different aspects.
Context is king. What's your employer's rationale behind certifying folks in an already pretty demanding(getting big radios wrong means potential surprise cooking of kidney's and the wildlife) discipline in cyber security?
I assume you're still happy there, so perhaps if you can understand why it's important such as bid support, diversification wanting to have enough cyber security employees so they can get acquired by Facebook etc - I'd suggest looking at associate of ISC2 or SSCP as a first step if it seems to align with your career plan and your employer can give you the important 'why' they would like you to take cyber security courses(I note they were looking at 'courses', rather than certification).
Lastly, this might be a personal thing. What do you want to do with the knowledge/contacts etc from the InfoSec world? I wouldn't say you're wasting the investment if you can't certify now it's aligning to where you want to go, especially as there is a wealth of knowledge on the subject you can pick up from just investing your time.
It' about the journey not the destination. While preparing for the CISSP was difficult and being awarded the designation is gratifying, the value was in the knowledge that was acquired. That is knowledge you can apply toward your current job. Every section I studied from the various texts and online sources, was something I could immediately apply.
Remember that whatever certification you peruse, ultimately you are looking to acquire knowledge that you can apply right now.