My ex got her masters in script writing, directed various small productions and was a producer for one of the major animation studios. So I'm basing my comments on discussions with her as well as folks who have taken gaming projects to profitable sale to EA.
Game development (for serious games vs. casual gaming) is more like movie or TV production. And from your comment about "simple UI screens created by a tech artist ot get the idea on paper" suggests to me you aren't even at Step 4.
So its way too early to be talking about a "prototype" or "MVP" . It really sounds like you have a log of work to do before even #2
My take only...and somewhat "counter culture" to gamers...
Figure out how the game will be compelling to play and addictive to return to FIRST.
If you can't figure this out no amount of stunning and incredibly gorgeous art will make a difference in the long run, nor will an easy to navigate UI (and all other "ui" variations), crystal clear online tutorials, appealing in-game incentives, "play everywhere" cross-platform capabilities nor... and the list goes on. Your churn rate will be sky high and your marketing budget will be spent acquiring players versus retaining players, with the anticipated disastrous effects on cash flow and ultimately the company itself.
As they say in Texas, no amount of lipstick will make the pig pretty. Seen it happen...