I think the alternative is an entirely new aircraft. And while that technically would be the most optimal solution, it's not the trend. "If it ain't broken don't fix it" seems the more popular phrase.
Apart from the control issue of more powerfull engine (extra tail length helps btw) strengthening (lengthening?) of the wing & pylon, changed blade separation requirements, heavier LDG etc. rotation angle will be smaller, probably requiring (Flap?) mods too.
Still an upgrade probably beats an 8 year E7 billion full blown development program. OEM's have become risk averse, cash tight. The ATR -600 upgrade (glass cockpit, new quiet cabin, better engines/ props) seems to have pushed the Q400 out of the orderbooks lately. Little incentive to get creative..
Bombardier has been caught napping, high performance seems lowish on operator priority lists.
