I feel that one CAN be a Mecha-suit badass, however their strength must not be solely reliant on their mecha-appliance.
For instance, in District 9, Wikus was not a badass, but he did cool things with an alien suit. Koobus, the MNU commando captain, was a badass by himself (despite being an insufferable bastard) - had he entered the alien suit (and somehow made it work - furthering his status), his badassery would be maintained.
Simon from Gurren Lagann is not a badass - his genetic gift is irrelevant without the Lagann, thus his power is solely dependent on the plot-tied mecha.
Fei Fong Hong (WONG FEI HONG!) from Xenogears is a badass without his Gears, as his martial skills (and later chi abilities) decimate opponents. Within his suit, he is colossally powerful - and eventually damn near unstoppable (on that note, most of the cast of Xenogears follows this pattern).
John 117 (Master Chief) was chosen for his genes, trained to be hard as nails, then genetically supplemented and re-grafted to be a penultimate combat badass. He was then given a suit of armor that cost as much as a UNSC cap-ship and made to do superhuman things. Now, the gaming world largely knows him solely for the armor (Bungie's 'It's you!' marketing strategy), but he is, in principle, one of the very, very best that was produced between Project Orion and the Spartan III program. (Still second to Fred, though...)
Samus Aran is not a badass. She has resolve and strength of character, but all her abilities stem from her armor (including the Zero suit). The friendly neighborhood Lombax is a greater badass than she - and he's reliant on his weaponry as well.
The Adeptus Astartes (Space Marines) of Warhammer 40K are badasses because they follow similar rules as the 'Chief - post-human war constructs in service of mankind; the trained super-elite that decimate armies. True, they are reliant on their equipment in-game, but in concept of fiction, they are quite effective without their gear. (Two hearts, waking sleep, spit acid, etc.)
You can kind of see how the pattern emerges. Sure, favorites want to be hailed as badasses, but the question is 'How much of a crutch is your mecha?'