I would suggest you've been offered an opportunity to diversify that many would relish.
Take it !....
As has been stated, employment is cyclical, remember after 9/11 the proverbial bottom fell out of the maintenance world and it took several years for employment levels to be restored. Since then, there have been several well known airline failures plus manufacturing cut backs and redundancies. In the near future, there's going to be a surplus of aircraft maintenance and aviation related engineers with little or no prospect of regaining a similar role.
You can always retain your interest, and participation, in aviation as a volunteer at a museum, and they would be delighted to see you, but frankly as I say, you've been offered a golden opportunity to diversify into another sector, gain new skills and experience and thereafter diversify further if you wish. One question therefore. With this new role, apart from the training required, are they offering any formal qualifications which would be recognised by, and portable to, other potential employers ?
If so, that's another very attractive reason to accept their offer. The long standing problem with the Licence is that, whilst the depth of knowledge and skills required are extensive, the downside is that it's exclusive to aviation and, whilst more employers may now be more aware of the criteria required to obtain one, many are not.
The "allure " of maintenance will always be there for prospective engineers, it's the reason most of us became such in the first place after all, but the prospects are now no longer as extensive as they formerly were.