Hi , i like how you change pvp options , so i hope this idea like you . I suggest to make a independent trade section for all sell/buy pokemon/items and auctions shown in photo 1 .
I made a simple desing of it to show better what i mean. On image one you see to main options: sell/rent and buy.
In the first section there will be several sub options: sell, lend and auction.
In SELL option will be : pokemon for sale ( can be drag from pc or best 6 ) and the price the seller looking for .When some pokemon is drag for sell , he will be locked till some buy him. The same will be apply to the items, where the number that the seller wants to place on the market can be added.
In LEND option will be: pokemon who you wish to lend , time interval ( i miss to add this on the image ) and price that you looking for.
In AUCTION option will be: pokemon ,option for starting offer,option for minimal bid, current offer, by who, time left of the auction and insta price button. If its make it right this will generates auction market to which every one will be able to bid for the given pokemon in time. The winner will be announsed automaticaly after the end of the auction and if the seller and the buyer are not online , they will be notified by message.
In second section will have : search , selling pokemon, buyng pokemon and auction.
In sub option SEARCH you can search for the appropriate pokemon or item you want, and the results are dispayed .
In sub option SELLING POKEMON you can see what pokemons are on the market , price and you can buy them directly with the buy button .
Similar information will show under the RENT option.The difference is that you will be able to take a given pokemon for a certain period .
In sub option AUCTION , the auctions will be visibale and buyers will be able to easily bid according to the initially set options or instantly buy the given pokemon within the auction.
This is my idea, i hope you like it. The images i attanch are to give you better idea of what i mean.