Heh, great minds think alike I guess, because I was also thinking of riffing off the original designation. The one that springs immediately to mind for me is The Axe, for obvious reasons, which isn't half bad. (Possible Crew name as the Lumberjacks? Not sure I love that one). Similarly, The Tax, but I don't like that one as much. Tank 1A may also be written as T1A, which looks very similar to Tia, spanish for "Aunt," which is something I could see a tank crew calling their machine.
All that being said, and I know this is wildly uncreative, but I've kind of come to just like "The Tank." I'm not as crazy about simply "The Crew," but it's not terrible, and I like that they're both so generic, which sort of enhances how exceptional they are - if someone is just talking about "the tank" and/or "the crew" and everyone knows who what they're talking about, that must be something pretty special.
For something a little more inspiring, there's "The Survivor" or something similar but quirkier - "The Outlaster," "The Endurance," "The Sustainer," etc.