It is certainly true that people take Stevens 200 or Savage 110 rifles and make super shooters out of them. But some things will never change about those cheaper rifles. When I look at the quality of the receivers and the way the bolts work with those receivers compared with my Savage 12 LRPV it quickly becomes obvious there is a difference. I have a 110 also. It's a fine rifle and I'm sure a new trigger and barrel could make it shoot great. But to shoot as well as my 12 it would take a lot of money. The trigger than came with my rifle is available for example. It costs over $500. And to get a barrel that is equivalent to the one on my rifle is going to cost at least another $400 (it's a stainless bull barrel 26" long). So already you are in the same price range as the 12 and you don't have the extra lug on the receiver among other things. It just won't be as good as the 12 LRPV IMO. It may shoot well and it might not. With a stock Savage if it doesn't shoot right you send it back to the factory and they fix it.
You will have some parts left over you can sell for scrap I guess. There isn't much call for a stock Stevens 200 barrel or trigger.
So you've paid about $400 for a 200 these days, you added $500 for the trigger and $400 for a barrel and now you need a stock that is equal to the H-S Precision that came with my Savage. Trust me my 110 stock is nowhere near the same level of quality. A H-S Precision stock runs about $400. So you have $1700 in a rifle that isn't as good as
the $980 LRPV. It would have to be some serious personalized advantage to get me to go the upgrade route trying to get in the ballpark of the 12 LRPV. Remember you still only have 2 lugs instead of 3 and the bolt is much heavier and smoother.
This is why I buy my rifles already built to be good. I've modified a few and it is fun work. But there's no logic to it other than the fun of doing the work.