Having traditional trading platforms accessible through Telegram mini apps will not only make these platforms more accessible and save space for apps download but will provide opportunities for newbies and airdrop hunters to receive airdrops cos these trading mini apps come with reward to incentivize users.
I could only think a mini version feature for trading might be possible knowing that exchanges have its own api to start with for different features including safety and security of their funds mainly hot wallets, if they will apply it on third party apps it could lead to potential risks ssince you will need to trust telegram with those information.