First off, the exploring bit.
I think you havent seen what i meant, people would explore, but the same dungeon over and over again, giving no place for other dungeons that might seem harder, less fruitful or annoying to them. A clear example, was when TC got released, that made everyone who went to HT for missions, items and else migrate to TC in a spamish way, thus leaving HT only for those who either want to complete it once (just once, that is), or get a pokemon like bagon from it, making them go to HT even though there are better places to go, much less annoying. This would apply for dungeons like SFR, especially center, which is annoying to first, reach, then explore due to strict restrictions (unless you have a nice pokemon for it, but it has gotta be high level and whatever else). And make places with rare pokemon, but easy (Like SR with kanga and else) get spammed all over (I found 15 kangas hunting one single TM rock slide ._.) to trade quantity (variety) for cuality (The 1-1 trade stuff wont be valid as counter, since even in items we do like 50 honeys for money). Why would anyone need to go fetch a rotom at tanren masion if you can trade a kanga, a tangela and a drifloon, or any wanted pokemon, or OU one for that electric ghost thingy? And if the user doesnt agree to it, one keeps adding stuff making it long and annoying
Rare pokemon stop being rare if the dungeon is easy and everyone does it. It is by pure chance, and it is a rare chance, but if instead of going to 10 dungeons, you go to 1, well, the chances up by ten.
Whiiiiiiiiich leads us to point 2.1 : Yeah, rotom in this case would be really rare (compared to the rares that are easier to get and spammed), and since you only add information and not what you want, people would only browse it for a fast trade, while they would try to convince those who has it and didnt post it there, going back to the whole trade stuff which annoys so much (Lets face it, there is ALWAYS someone who harrasses for something they want practically for free, and this cannot be controlled by auto mechanism like bad words, so it must be screenied and reported, and to show that it really is extensive, a load of screens would have to take part)
Point 2.2: If you add information and you add the pokemon you want, two problems might rise:
-People ask for ridiculous stuff like in GTS, therefore it fills up a space that nobody cares about (either troll or in a nub hope you will get what you want)
-Since it would be a pokemon so rare, what would you even want to trade it for? Another rare of the same chance might result, but then again, who would have that too, the specific rare you want and would like the specific rare you have, leading to yet again it being in there forever.
Lets be honest, the trades for uncommon pokemon would be next to none (after all it takes like 2 runs to get one if you are seriously hunting it), this is all around the rare ones. Common ones wont even have aplace in it, except for newbie trades and the usual trolling.
Plus, would the information you add, data-wise, meaning you can only add what you have (kinda like GTS), or that you can type exactly the information, letter by letter? Which i already mentioned before, the negative traits both would bring up
It might not be heavy in that manner (Plus it wouldnt have major glitches), but i dont really see that many people complain about not being able to trade, (usually just people angry that they cant get a pokemon and lose their minds, some people gotta understand the meaning of rare and luck and that it sucks for most, including myself) what is more, it makes the community more peaceful and quiet in economic terms, which is one of the reasons i addict to PMU (I might be greedy to the point of not giving rare items and wanting to buy for cheap prices, but that is one thing and another is when you rip off -not that it doesnt happen in PMU, but in a whole different number- , or ask for more freebies from someone who had a goodwill towards this person, or people, that is, again of the agains, annoying)
Plus i wanted to throw out there, that even though its not my idea, i agree to the whole thing of the pokemon that joins you, does so because it respects you. Its not like im not aware its by pure chance, coding, numbers, that they are pixels and whatever, but um, yeah. A pokemon in PMU joins you and you are the pokemon itself, making it awkward to trade yourself :S It would be like trading accounts in other games, or in the original ones trading game cards. That the pokemon joins you because it respects you is the story of the game itself, it might be chance, but um, yeah.
Again, just the barbaric opinion of one who has been through hell in an economy based pokemon game. (and sorry for the unusual long posts coming from me, but that place traumatized me pretty much)