Here's something to consider when thinking about performance parts. I know it's a big consideration when you hear that it wears the engine faster (believe me - I resisted as long as I could) but there are some un-spoke of benefits too.
1.If you already have a performance pipe (and I hope a re-jetted carb.) you are already "damaging" your engine. The pipe widens and increases the power band on your bike by supercharging the engine from the exhaust side, instead of intake side. You are now running the engine at higher rpm's and have leaned out the mixture by the addition of compressed air, which creates more heat, etc., etc., and leads to more engine wear. So you are already "damaging" your engine more than it was design to.
2.You probably already ride at full throttle for long periods of time (An unfair assumption but why would you be looking to go faster if you weren't). If this is the case, you are pushing your engine to the furthest point of what it was designed to do. Now, if you replace the cylinder, cylinder head, and piston with a standard bolt on kit (with a stock exhaust), you now have an engine that was designed to have more power. More power means quicker acceleration and that you can power higher gears (= more speed). This setup is now designed to go at these higher speeds and will work accordingly.
3.Now here is the problem....You take that higher power engine and put on the performance exhaust, and all of a sudden you can ask more of the engine than it was designed to do...but it still will. My point here being that you could do this with the 50cc engine also, but you didn't seem to be too worried.
4.Performance parts require a lot of messing with to get dialed in. i.e., you will need a larger carb that you will have to re-jet etc., etc. The thing is, there is very little documentation that says "put this pipe with this big-bore kit, with this carb., with this jetting at this elevation." It takes a lot of heartbreak (my experience only) to get it right.
5.If you do get the thing dialed in, it won't do any more damage than you were willing to do by adding the performance pipe.
6.(Not that I'm rich at all) but parts are "relatively" cheap for mopeds. I think cylinders at around $50 and pistons are say $20. And having an engine rebored costs less than $50. Just remember it's an investment and fifty bucks ever two years for a rebore isn't that bad considering how much fun you had and how much you saved in gasoline. I say do it. It's great to feel like a grease monkey. Good luck.