Well here is another tidbit that you might want to consider.
ELTs have to take the MM test for advancement all the way up to E7. There is tons more MM stuff on those exams than ELT stuff. As an ELT, I seriously doubt you would know the little nuances of putting on a mechanical seal for a pump, the aspects of filling out a QA-2, or other Mechanical Maintenance stuff. Not to say that all those things could not be overcome(thousands of SMAGs do it all the time) just that it is a little more difficult. Of course you could volunteer(

ELT volunteering for extra work

) to help out M/RM with pump overhauls, valve repacks, etc.
On the flip side, when you go to qual for EWS/PPWS being an ELT does have its advantages. That is probably one of the harder sections of Sup Quals is Chem/RadCon.
All in all based on what you told me, you would be a waste as a SMAG(if you don't know what that is, it is a look up NUB. And you better bring a cold beverage with you when you get me that look up. Mt. DEW or anything not diet!) Now fair warning, the "fun" maintenance for MMs is few and far between. You only get to tear a pump completely apart every once in a while for PMS or when it breaks. Most of the time it will be some BS small valve maintenance or blow down this air tank or even blowing down the EOOW(snicker, snicker).
Forget the SMAGs and go Mdiv Tough.