Dopterians are physiologically similar to Ferengi, and most of the Dopterians encountered have been criminally-inclined (thieves, pickpockets, and even a co-conspirator with Lursa and Bator). However, there have also been exemplary members of Dopterian society, such as gymnasts and ambassadors. Not much is known about them in canon, but they cannot be read telepathically in the same way that Ferengi are immune.
The Dopterians have been known to the Federation for a long time, since 2245 at least (as established in beta canon). They originate from the Alpha Quadrant. They could be great substitutes for those who want to play a Ferengi-like character in a pre-TNG era.