My thoughts on MVPs align pretty closely with this post: https://hackernoon.com/the-mvp-is-dead-long-live-the-rat-233d5d16ab02#.rt76og5qu
Essentially, can you first confirm that the “situation-switch” you’re looking to provide is something that people even care about?
It reminds me of a “Lean Startup” story from a while back (which I can’t seem to find) wherein someone thought they could build a business around selling cars over the phone. Rather than create all the infrastructure, and purchase cars in volume, and hire a ton of operators, etc. before finding out if it would work, they first put out a single classified ad for one specific car. When their ad got a phone call, they fielded the sale and drove the car to the new customer themselves. Only AFTER they validated the demand did they invest in scaling out the service.
This is all to say that when you ask about when it’s appropriate to “fill the gaps”, my answer is “always” — it’s just a question of whether you’re doing so with elbow grease or technology. The smart people always seem to hold off on the “technology” part until they’ve confirmed that there’s something to scale to begin with, though.