There's more to ThinSkin bases than meets the eye. Yes, a really thin base will disappear better than a thick one, but there's another factor to consider: density. The base must be thick enough to support the client's specified density. Each hair injection creates a hole in the base and the higher the density, the more holes per mm. If the base is too thin, it will tear easily. So even when you specify the base thickness you want, a good factory will make sure that the base is thick enough to support the density - even if they have to make it a bit thicker than you requested.
As far as the value of adding extra holes for ventilation, this is a bit of "spin" on the part of certain manufacturers and sellers. The holes, by necessity, are so small that they make virtually no difference in the comfort of the system because very little heat can escape. Also, they're so small that water can't pass through them. In other words, perspiration will still be trapped against the scalp and showering/shampooing will not clean the scalp.
I believe that hygiene and cleanliness are very important - and rashes and infections are really ugly.