Related (but different from) some similar ideas already suggested, I would like a user controlled set of aliases, so that I could define a set of utterances that should automatically map to a custom skill.
So, for instance, anything starting with "remind me" gets forwarded on to my own skill such that saying:
"Alexa, remind me to buy some stamps" would automatically get treated as if I had said "Alexa, tell MyCustomSkill to remind me to buy some stamps"
Then I could speak to my custom skill as easily and naturally as I normally do to Alexa, and I could override the default handling of any (start of) phrase that I want.
My current custom skill does a lot of things, including handling reminders in a time based way, so that I can ask it to remind me to do something when I leave the house (or when I get in, or when I get up, or on Tuesday evenings etc) and then when I later tell my skill that I am going out (or have got back, or am getting up, or have come back in and it happens to be a Tuesday) it pipes up and reminds me of what I might otherwise have forgotten.
This alias method would mean that not only could I just say "Alexa, remind me to put the bins out on Tuesday evenings" but I could also say "Alexa, I'm back" and my skill would instantly say "Welcome home, don't forget to the put the bins out", without all that tedious "Alexa, tell Gideon that I'm back"
My skill is a development only skill (I have no intention of releasing it to the world), and so I can't see any security implications of me being able to create overrides in this way, and it would massively improve the usability of Alexa.