to be perfectly honest, this would make the gts grind completely to a halt. While I do agree completely we should be able to see a summary of the pokemon we trade with friends, on the GTS that would be incredibly limiting. You can disagree all you want, but how many times have we all been ont heir looking for a particular pokemon, find it, only to discover they ONLY want a (for example) male charmander between levels 11-20, and we have 50 charmanders but all the ones between 11 - 20 are female, and all teh males are level 10 or 21+? having MORE limitations on the GTS would just clog up the systems and eventually no one would be trading on it anymore. (Oh, you want a level 23 exactly Darumaka with an Admamant nature, it's hidden ability, stats ranging between this and this, and holding a Fire Stone? Sure, I have one of those just lying around!) Don't use sites like this to gauge the pokemon community, the vast majority of people don't actually care about the natures or stats as much as they care about getting just that one particular pokemon they really really like, or because they want a pokedex entry or whatever. The GTS is geared to get you the pokemon you want, not an incredibly filtered net of crosshatching conditions to get EXACTLY what you want. You found the pokemon and now if you want a particular nature or IV spread or moves, then you need to work for it. That's what every pokemon has been about. Do they make all wild pokemon level 100 with 31 IVs in every stat and a competition ready move set or do they just provide you with wild pokemon with random natures and stats and then it's your job as the trainer to build them up the way you want them? That's what the GTS is an extension of.
Having said that, there is one feature I wish the GTS had and that is when you HAVE a pokemon and you see what you can get for it (So you select one of the pokemon you have, then you get a list of other people that are looking for that pokemon and you choose out of what you can get for what you are offering)