Congrats on finding the right gal! There's no better feeling than realizing you've found the woman you want to spend the rest of your life with.
I think it's a great idea (assuming your soon-to-be-fiance is on board). My wife and I are in the wedding industry and attend 40+ weddings every year, and it's unbelievable to see the amount of money spent on a single day. You've probably already seen the statistics on the success of a marriage vs. the cost of the wedding, so I won't bother going there.
My wife and I got married three years ago and stuck to our budget of $5,000 (over 60% of that was on the photography). We kept it relatively small with 75 guests. We decided to do a chili fest, which meant that we cooked up a handful of our favorite chilis, and we also asked a handful of our friends and family to cook and bring their favorites. Some had beef, some had chicken, some had bison, some were vegetarian, some had beans, some had no beans, some had chocolate. It was a fun spin on the traditional wedding dinner, everyone loved it, and it only costed us about $4 per person (compare that to the national average of wedding dinner, which runs $85 per person). We also spent about $500 on beer, wine, and whiskey, and had plenty of leftover to last us for the next 6 months.
My quick two cents:
1. As you already mentioned, don't skimp on the photography. The photos and the memories they'll hold will be worth more than gold and you'll cherish them forever. Even on an extremely tight budget, we allocated $3,000 to photography. At the very least, you could hire a professional for your ceremony (however brief it may be). If you need any help finding professional photographers in various states or countries, feel free to PM me.
2. The best time to buy a wedding dress is fall / early winter. That's when places are getting new dresses and clearing out last year's dresses.
3. Remember that it's your wedding. Everyone is entitled to their own big day, but you can be certain you'll hear everyone's opinion after you propose. If someone doesn't like your unconventional approach, they can go get married themselves and have a conventional $50k wedding and blow all of their money. It's simple advice but it can be tough when you're getting pressured by the people you love the most. Stick to your guns--you have an awesome idea.