* A cardinal law of nature is: Anything that can be eaten, eventually will be eaten. Even the noxious species usually have a few predators. Owls eat skunks. Monarch butterflies eat milkweed and use its chemicals for their own defense.
Therefore, somehow, somewhen, species must learn how to eat new foods. Perhaps this is a process that can be speeded up.
(I do not advocate gengineering as a solution, because people are already being irresponsible with it. Conventional training or breeding methods are much safer.)
* Strategies for selecting possible eaters based on breadth:
1 - Choose generalists. Some species will eat pretty much anything they can fit in their face. This requires a minimum of effort to set up.
2 - Consider specialists, particularly those suffering a dearth of their preferred food. Do a biochemical analysis of the invasive species. Compare the results to other species and identify the closest match(es). List the species which eat the matching ones. Try to get them to eat the invasives. While this is slower, more expensive, and more difficult than choosing generalists, it has a potential payoff in supporting desirable specialists.
* Strategies for selecting possible eaters based on origin:
1 - Choose only native species to eat invasives. Natives are more desirable, and many of them need all the help they can get.
2 - Choose other invasive species that are already ubiquitous, such as house sparrows or starlings. Those guys will eat French fries. If they're going to be here, they might as well make themselves useful.
1 - Use a semi-voluntary feeding pattern. Offer the invasive food first, at the beginning of every meal when the eater is hungry; but if they don't eat it, later offer other foods. Another option is to grind up the foods, mixing together several types. Add a little invasive to one dish, and not to another. See if they'll eat it. See how much you can sneak in before they quit eating it, if they do.
2 - Attempt to raise young eaters on a diet that includes invasives. Can they survive on such a diet? How high a percentage can be invasives before it starts having negative effects on health or survival?
* Observations, developments, and outcomes:
1 - Are there differences among the various eaters? Do some individuals resist strongly or sicken, while others are more tolerant or even eager?
2 - Ideally, breed the most tolerant eaters to each other, working toward even more tolerant offspring. Remember that it only took about 60 years for Russia to domesticate foxes.
3 - Seek to establish a population of invasive-eating individuals in the wild. Hopefully they will pass on these traits and genes to their offspring, thus creating a natural control on invasives.