Additional oil cooler is the answer (whether watercooled or Aircooled), not more air, and only if the engine does actually overheat. Bear in mind engines run at their best when up to operating temperature which is fairly hot. Making sure the seal around tinware and engine bay also helps reduce temperature - as does any heatshield fitted above exhaust. VW did all this stuff in the design/testing. Its only when you depart from the norm that you have to rethink things.
With your 2.0l, just make sure the seals around spark plug leads (tinware) are there or replaced. engine seal in place and you'll be fine. Its an efficient system considering its simplicity providing nothing is missing. The 2.0l is basically just a larger beetle engine with the cooling system flattened so it all fits in engine bay under the hatch. The longevity of the beetle lump is legendary. Its basic engine case design remains in the later 1.9 watercooled engines with exta cavities to force water through. The T25 is basically a beetle in a big dress
The drawback with the 2.0l is there are less of them and bits can be more expensive as a result (some parts now obsolete). However, the gearbox bell housing is identical to that found on a bug or type 2 and I once fitted a bored-up bug engine in a T25 crewcab where the engine lid is higher, with good results. You need the 1.6 Aircooled engine carrier and an adapter that bolts across oil cooler to get the fixing points. A flywheel change, hand-cut tinware and custom throttle cable completed it. The main advantage was cost of spares - half that of a 2.0l engine and much easier to work on. Its not possible in a regular T25 due to height restriction unless some kind of elevated box is fitted where hatch is. Would look kinda silly too.
In summary, if you're overheating, figure out why and if you really do want to improve cooling, fit an external oil cooler but its not worth it if there is nothing actually wrong with what you've got.
Hope that all helps.