I haven't"scheduled" anything like you are shooting for, but The YONOMI app appears to have the capability. They have pretty decent Customer support, however, it's slightly convoluted. Their email sends *me* a "message unable to be sent" thing, and I get a reply anyway after a couple of days... Evidently they get the email, but their server sends out the fail messages every time.
In the App, it appears that you can choose a date and time for an event... or set a location (for your mobile device I to arrive or leave a location), and Conditions that make it a valid situation... Now it doesn't give commands to everything Alexa can do, but it will command items set up in Yonomi... Like Hue Lights, or Your AV system... I understand there are about 90 items that are associated with YONOMI at this time, so anything that's added must be somehow linked as well. I have Hue Lights... but do not have them set up through YONOMI, as Alexa does fine without the added app on that particular item. If I wanted to Schedule a light to come on at a certain time, I would add those to Yonomi for sure.
I know it's complex, and not super self explanatory... but once you get the YONOMI app working it's a pretty cool app.
Edit: I actually set up my Hue lights while I was writing this post as well as my Thermostat (Honeywell Lyric) and both have options like I thought they would. Yonomi Discovered and linked to them all pretty much effortlessly. (as long as you know your account email and passwords...). Looks like a solid set up for just about anything.
This is all "IF"... the location is US based... I know things work . similarly in the UK... but have seen some things that don't work the same for one reason or another.
The "one time" commands... well... I don't see it happening without Alexa Updates... but I like that concept as well.
Maybe with the IFTTT and YONOMI both... it could happen.