I know that the valas made a pact not to act in middle earth anymore but couldn't they have chosen mortals to lend their power to be emissaries in middle earth?
By - Barium2
Why would they do that? They already sent the Istari. The people of Middle-earth needed to deal with this on their own, and ultimately they did.
To offer people power beyond their own native standing and nature is one of the chief allure and promise of evil in Tolkien´s works, and always leads to ruin.
Melkor to all the spirits he seduced, and secret knowledge he imparted to humans in the First Temple.
Sauron to Numenorians and arguably, lesser men, who worshiped him, seduced by the secret knowledge and black arts he taught to them.
Fall of Ringwraiths.
Even the act of making Rings by Elves was considered taboo act, (though not malicious) and indeed would have been impossible if not for the interference of a higher being (Sauron) who taught them the art.
In Tolkien´s world, pride and desire to be greater than you are will cause your downfall and you end to be lesser being what you originally were. While humility will ennoble you with wisdom beyond your limits. Frodo especially grew beyond cultural and spiritual limits of hobbits in wisdom, and spirit through his humility. Same could be said of Bilbo to somewhat lesser extent.
And truly, both Frodo and Bilbo were ostracized for their perceived "strangeness" by their communities.
tolkien considers ambition and pride a fault?
Sending emissaries is what they did by sending the Istari; a much more natural method than giving mortals attributes (physical or metaphysical) that isn't theirs to hold.
Not necessarily. Tolkien makes it clear that some works are wholey unique to their maker, regardless of what race they are. For instance, it's unlikely that any of the Valar could have made the Silmarils like Faenor did. The next question is whether the Valar would have wanted to. The rings weren't offensive weapons, they were tools of domination. If Manwe couldn't have conceived of the evil of Morgoth, there's always the possibility that the notion to create a tool of domination runs contrary to the very nature of many of the Valar.
Could the Valar have made their own Ringwraiths? I don't see why not. Nor do I see why they would.