Steampunk, delightfully, does not follow that law!
I'd advise STRONGLY against the bikini. It reads "wrong" for a few different reasons--an actual engineer would want more protection, a lot of newcomers to steampunk go for 'sexy' steam and end up looking out of place, it's from a much different time period than steampunk's Victorian roots, etc etc.
MPsy's suggestion of a flight suit or coverall is great, I think. It's a very practical, authentic garment that hasn't changed much in design since that time, and scuzzes up SO nicely if you get one in cotton instead of a synthetic fiber. You can also wear nearly anything you like underneath, and undo the top to show it off. A corset and chemise? Work shirt? High-collared blouse? Whatever you want, it works.
An engineer has every excuse to go absolutely nuts with big gloves and goggles and boots and any little tool you can hang off a belt by a leather cord.
Don't pass up the chance! Details really fill in an outfit and make it look complete.
And don't forget weathering. It looks from your illustrations like you're comfy getting some soot and schmutz on this outfit and that's brilliant! Here's
a good place to start on good techniques for distressing clothes.