She is perfectly reasonable, I guess, to ask me to reign these plans in if we have a kid, which is why I'm 'scared' I guess,
Well, there's reigning in, and there's reigning in. Is she asking you not to do it quite so often, or bin it off entirely? One of those is reasonable, the other not so much. And would this be for ever, or just for the first year or two after birth? Does she only want the one?
You've held down a long-distance relationship so presumably being apart for periods isn't the problem; that won't change just because you've signed a bit of paper and had a big party. So "raising a family" is the elephant in the room here.
is it a pre-requisite to a happy marriage that I WANT to get married now, or should I just man up and hope that once the sprogs land I'll not miss the stuff I'm so worried about losing right now.
Moreover, are you going to look back in ten years and decide it's the best thing you've ever one, or resent being tied down?
I'm kinda torn on this. I guess the bottom line is that you can't foresee the future and only you and her know how you both feel. Ultimately, you need to be working towards something that makes you both happy; strikes me that your compromise here is doing what she wants rather than what you want.
"Traditional" relationships quite often had situations where the woman was the home-maker raising the family whilst the man was often working away earning the family income (or being shot at). Of course, in these modern times the lines are blurred somewhat, and both partners typically share both working and parenting duties; point is, there's no reason at all why that sort of model couldn't work for you if it were something you were both happy with. She gets a marriage and a mortgage and 2.4 kids, and a loving husband who's around "most" of the time, you get a family to enjoy and the freedom to pursue your life goals and advance your career. Maybe.