We don't intend to add this no.
Being able to recover your bitcoin, in extremis, from your wallet words is a real life saver.
With Classic support calls we would always ask if the user had made backups. I only ever recall ONE person saying that they had, normally the reply was a deafening silence.
We call it the 'wallet words promise'. As long as you write down your wallet words and keep them safe, you can get your bitcoin back.
I understand your concern, but I don't want to be unable to see my transaction history.
Could I suggest a "spend at import" feature, you add the possibility to import an old key (for see its transaction history and don't loose future payments) but you "force" to send all unspent money to a "Multibit HD address" when you import it.
With future transactions to those addresses, you could use "that money" first in any future transactions always sending the "change" to a Multibit HD address
Cheers
MC