The trim will not snap if done right and the glass will not bow just from removing the bracing. When you de-rim the purpose is to add euro bracing. Without it, yes it could bow once filled with water. The only way to go without euro bracing, it to have thicker glass. Since the tank is existing, thicker glass is out of the question. Euro bracing just gives you that cleaner look which is why people do it. Don't go without it on a 6ft tank though.
I did de-rim my125g tank I bought on craigslist last year. It only cost me 60 as it was scratch up fairly good. If you have patience, it would go smoothly. I got near the end and rushed a bit and I got careless. I ended up breaking off a piece of glass on one top edge but it was clearly my fault. It was only a 1x1 triangular piece that I was able to silicone it back in place. This tank was going to be used as a plant only grow out so I wouldn't fill it all the way to the top.
To do the task, you need a strong long blade utility type knife and a hacksaw. Break the silicone seal on the inside and outside. You may want to score several times to be for sure. On all four corners, use the hacksaw to cut the trim in two places. This allows for easier breaking of the trim. Also cut out the bracing in the middle. I did this on 3 corners of my 125g and it worked great. For some reason I got careless and I used my angle grinder and cut the trim on that last corner. Well, the blade cut thru the glass and chipped out that triangular piece I mentioned. If you want to retain the trim, you will have to really go slow and take your time. You must break the silicone seal completely or else you could snap the trim. I used this method to de-rim (4) 40g breeders as well and it worked great. I didn't want any of the trim so I did snap mine. Just avoid prying too much against the glass. The thinner the glass, the easier it is to break/crack it.