It could work. RPGs, at the end of the day, are roleplaying games, not "level up and point spending games." The hard part, however, would be to have that sense of progression. If you have the sense of progression only within the story, then those not as interested in the story will not have much reason to play, and you've just essentially done a disservice to them.
So there would have to be some mechanical milestones for progression that the player could cling to. What you would do in that case instead of xp/levels isn't really something I've thought long and hard about, so it's not really something I could brainstorm right now.
Simply stating that you want the game out of the way of the narrative is one thing, achieving that is another. Such rule-sets require a lot of GM interpretation. If all you have is combat rules, then you haven't finished your mechanics. What about non-combat related skills? Do you want players to persuade/intimidate people through pure role-playing? What about players that just want to trudge through the game and have the persuasion come down to a dice roll?
In terms of publishing an eBook, that is the best course of action nowadays with the rising cost of physical copy production. But I think you are underestimating what your adventuring guidelines needs to entail in order to make this a system that will be attractive. Remember that the chief question you need to answering (especially with Medieval fantasy) is, "Why shouldn't I just play D&D?" If your adventuring guidelines are too simple and bland, you aren't going to answer that question.
Additionally a lot of what you may take as "getting gameplay out of the way of story" will come down to a lot of abstracts, otherwise, you will end up with a game that feels disjointed as the adventuring guidelines continually clash with the various mechanics. remember that the most important thing in an RPG is not story, but rather the enjoyment that the players have. Story should enhance that enjoyment, not be a bar to that.
Overall, to be perfectly blunt, I need far more information on the game to give you any kind of meaningful advice.
Firstly, if this is the first question you ask when making a game, don't get into game design. Game Design, like writing, film, or any art, is not a field you should get into if you're looking to make money. There are many fields that are far easier to get into and pay far more money. Do game design because when you think of what you want to do, you can think of nothing else you would rather do than make this kind of art.
With that said, the answer to "What kind of game will make money" Is fairly straight forward: There are two types of games that make "decent," money. Those that are good, and those that are marketed well. "Good," is relative, however. There are just as many that will say that CoD is the best game ever as there are people who will tell you that it is nothing more than graduated DLC being sold a new game, and thus bringing down the entire industry as a whole. So what type of game should you make if you want to make money off of your art? Make the game you would want to play with the resources you have.
Firstly, story is not what drives a game's budget. In most cases (outside of very select studios like Valve, Obsidian, Bioware, etc) story is done last. They make the assets, levels, etc for the game, and then a narrative designer is contracted to basically explain how everything fits together. This is the reason why so many game stories are either incredibly cliche, or feel tacked on.
Secondly, I have to disagree with you on how story should work. In Story-driven games, such as Dragon Age, The Witcher, Baldur's Gate, etc, the player knows exactly what they are getting into. They know that this is a story driven game. To say that this is unfair to the player, is similar to saying that a shooter is unfair to the player because it isn't a turn-based strategy game.
Games like Serious Sam where the story is just there to explain why you need to shoot stuff are not magically better games than story-driven games, yet you present the argument that the only games that should have story at the forefront are interactive narrative. I'm sorry, but this idea is nothing short of ludicrous. Can story be done better in many games? Yes, and one of the ways it can be done is by writing the story first and structuring everything around it, rather than the opposite way. Most games, as I said earlier, construct nearly everything about the base game before bringing in a writer. This, and not simply the presence of an important story, is what causes the break between game play and story in most cases.
Additionally, even in open world games or games without story, you still only have a set amount of ways you can deal with a situation. I cannot, for example, run up in Serious Sam and attempt to talk a Gnaar out of trying to kill me. My options are: A. shoot it; B. Run away while shooting it; C. run away. I have no other options than that. So to say removing story will add more choices allowable by the imagination is, sorry to say, quite ridiculous.
A video game is designed by a group of people who each have their own imaginations and ideas. Any game, regardless of the presence of story, will only have a set amount of ways you can deal with issues. Games that push story to the back can easier give an illusion of larger choice, but in many cases actually have fewer choices than in-depth story driven games. For example, let's take Elder Scrolls. When I get a quest I have two initial options: Run off and don't do the quest and just run around, killing things and looting things, or take the quest. That is a binary choice. Now when I take the quest, let's say I am told that I need to clear a cave of goblins. My choices are: Clear the cave of Goblins and Don't Clear the Cave of Goblins. Once again, I have a binary choice. Sure, in a game like Elder Scrolls, the combat system allows me to choose how I clear the game of goblins, but this has everything to do with mechanics and nothing to do with the presence of story or lack thereof.
Do some games work better without story? Yes, but to say that only interactive drama type games should have an in-depth story is nothing short of ridiculous to me.