You have no personal knowledge as to what DE intended; claiming you do suggests the rest of your point is similarly baseless.
We do know DE (a) intended for rivens to be tradeable between players for plat, because that's the system DE implemented; and (b) knew rivens would have a huge impact on endgame play, because they've spent significant amount of time and resources on balancing rivens on an ongoing basis. You cannot seriously suggest DE thought anything would happen with rivens other than players grinding for the most desirable rivens/stats, and those in turn becoming a significant portion of the player economy that is facilitated almost exclusively by purchased plat (non-purchased plat not being tradeable, and few trades being item/mod bartered for item/mod).
Accordingly, the most reasonable reading of DE's intention w/r/t rivens is they would -- whatever else they added to the game -- increase plat purchases, being the biggest (albeit indirect, as they're not sold by DE) P2W aspect of Warframe and players thus wanting to be able to buy them from other players. If DE wanted rivens to not become the dominant force in the plat-facilitated player economy that they so obviously are, DE would have made them like Umbral mods -- untradeable.