I've enjoyed
Tobias for quite a while. And I don't mind the nickname
Toby at all. Which pronunciation were you thinking: toh-BEE-us or toh-BY-us? It would be easier to aboid
Toby with the toh-BY-us pronunciation, but either way, I do think that is would be possible to avoid the nickname if he himself didn't like it and always introduced himself as
Tobias. But you must always keep in mind that you can only insist on it yourself for maybe 3-4 years and then he may just have an opinion of his own.
Guru's suggestion of a
Tobias J___ combo is a good one, I think. I love TJ as a nickname.