@jaberg: If your workaround works for you that's just fine I suppose, but it sounds pretty cumbersome - no offence, it's the shortcoming of the tools that make it that way, I understand that. But for me, probably I will stay with my MacBook. But especially when traveling by plane, taking both my iPad (for reading mainly) and my MacBook with me as I do right now is becoming a royal PITA, with all the restrictions re. carry-on luggage and so on.
As a last resort, I could imagine changing my workflow like this: Use the iPad just as a backup for the memory cards, and the keywords in LR for iPad as a scratch book or external memory, transferring them to LrC by hand at home. On the other hand, that's quite a price to pay for not having to lug around the MacBook in addition to the iPad.