If you do decide to get tank-mates, make sure they are not big enough to eat the eel or the eel is not big enough to eat them (Just a side note, if you want another spiny eel, I would not advise that. they do not do well with each other.)
The elephant nose is not really hard to keep alive, its just a sensitive fish. If you do decide to add one, make sure your tank is well established and be sure to keep up the water changes, doing them once to twice a week (they need perfect water). Make sure to have hiding spots, otherwise, this fish could die. Also, the elephant nose fish needs at least 50 gallons of water otherwise.
If you have enough room to house the BGK (100+ gallon tanks. They are known to grow a few feet in length), I would say go for it. Like the EN (elephant nose), this fish is also shy and needs hiding spots (also nocturnal).