I would not get a 5 euro hop up unit, that is not really an upgrade in anyway especially if the stock one works fine, if you want to change out your hop up unit I would rather take a lonex hop up which is more solid and well tested by many users. Has very small tolerances which makes you able to dial in the hop up perfectly with no side to side wobble. If you think the current one is fine, then rather do some small and easy DIY mods to get the most of it, for example look at hop up unit shimming, this allows for no side to side wobble if there is any currently.
V2 and V3 use the exact same piston and piston head, only things that are different are the trigger contacts, trigger, cut off lever, selector plate, motor, cylinderhead (replica related), spring guide, nozzle (replica related), oh and off course the shell
. Actually that is quite a lot now I think of it XD.
I would also not recommend 13:1 gear sets to people that have only one gun and never tinkered with it. Also it is not correct that KWA, KRYTAC and VFC use 13:1 gears, literally every manufacturer uses standard 18:1 gear ratio, I would love to see where it says any of these 3 manufacturers uses other ratio's regularly? 13:1 would mean you could run into PME, although on a 7.4 it is unlikely on a 11.1 it is nearly guaranteed, which means you need to short stroke, also on 13:1 you have to shim and correct AOE to not break the gun after a few skirms. AKA not really a recommendation for a beginner.
I'm not going to tinker with the gearbox just yet, so I won't need the gears nor the shims just yet... ROF is not an issue for me as I prefer semi auto. At the moment I'm content with my trigger response as well.
Would there be any benefits in choosing let's say a maple leaf cylinder, cylinder head and piston set?
In my honest opinion no, only benefit of a one piece maple leaf cylinder is that you don't have to worry about the air seal between the cylinder and cylinderhead. But most 2 O-ring cylinderheads and a decent cylinder can get a perfect air seal, I mean you don't have to upgrade even there are many DIY mods which also allow people to get perfect air seal with stock parts.
Also although this breaks my heart to say but skirmshop.nl is really overpriced for a lot of the stuff they sell. I still buy stuff there if I don't wanna wait and because they have really good customer support, they will awnser all mails regarding AEG upgrading within a day and explain everything to the utter detail (although not necessary for me still very good and kind of them). Lastly it is good to sometimes boost the dutch economy XD.
But when buying a maple leaf bucking, nub and a lonex hop up unit, you can't get that cheaper when buying seperately at different places.
But to go back to your initial guestion, which was to upgrade the range of your replica, so the only things I would consider then is a maple leaf bucking and nub, a lonex hop up if you think the current one is not functioning optimally and a barrel, because the stock CYMA barrels are just horrible but that is more for better grouping then the range, maple leaf or madbull stainless steel ones are a good mid level option.