[itsme]

My opinion about transposing is caused by the workflow that I use:
Setting the starting key is part of preparing a song. Create the file, transfer it to the tablet, edit the meta data, check that it displays OK. That's done at home, no problem to change tools, use a computer, think about what's happening. When this is finished, the starting key should be correct and will hopefully never need to be changed. So opening the file and adding {key: in case "Detect Key By" fails is not an issue, nothing different to changing a chord within the file or correcting a typo.
Transposing on the other hand is mainly a use case during a session. Someone asks for a different key or I notice that I'm in the wrong key for any reason. So this should be as quick and error-proof as possibly.
That's why I prefer to remove setting the starting key from the transpose dialog.