Ok, I am not very good with the vsr's but I know a few things. Alot of these upgrades are similar in function to those of the l96. They just are not compatible with the vsr's. To answer as best I can...
1. Fluted outer barrel: I believe it is better quality making it more durable.
2. You are correct in saying the bolt would be useful for when you upgrade to a heavier spring. This is to make it more durable to prevent it from breaking.
is what I believe you are referring to. I do not know much about it, but I believe other vsr users have this. Laylax is great, I use alot of their parts in my rifle.
4. I never put the spring guide stopper in the category as a sear. Maybe I am wrong. Either way, that would also increase durability when using a more powerful spring just like the trigger and piston sears will. I put a trigger sear in mine until I can get a zero trigger in the future. It really made trigger pull easier and smoother. But its totally up to you. Here is a link to a sears set (out of stock at the moment, but its just to give you an idea) : http://www.airsoftgi.com/product_info.php?cPath=362_364&products_id=5756
They also have some of the bolt action upgrades for your rifle if you want to look their too.
5. For the spring guide, I totally missed that. I am terribly sorry. I was just naming things off the top of my head, but yeah that would be good to get. I know that in the l96's, there is a 7mm and 9mm spring guide that are necessary depending on power. Not sure about the vsr's but just wanted to give you a heads up.
Hopefully someone can give you some more detailed info. I am just trying to help you get started off. I bet Vindi will either give more info or clear up some things that I cannot for you.
Hope this helped somewhat