The only solution I found to getting Generics into Domino is to not use them. This can be messy at best as you have to write type specific implementations for every possible type the method could be called with.
I would suggest explaining the compatibility issue with Domino and suggest to them they accept the .jar file solution as it is most reliable and least time consuming. They will save money down the road when they don't have to try to debug odd errors and if needs be, the source can be included as a file resource in Notes for their edification along with build instructions. I am assuming they want it self contained to avoid issues once your work is done?