For some people, turn-based combat also sounds so 1988 that they wouldn't want to play the game. Fortunately, that doesn't keep you from implementing turn-based combat in D:OS.
Money with weight makes the game world more credible, but it is a restriction or an obstacle, and as such, it doesn't make the game more interesting - unless there are counter-measures like valuable (but light) gems, banks, or money caches. If money with weight only leads to a permanently lowered carrying capacity because there's no clever way to store your riches or to reduce their weight, it's a bad idea. If the games offers such possibilities, however, it can become more interesting.
Since you seem to find it difficult to balance the game for casual and hardcore gamers alike, why not offer several difficulty options? Like "easy/medium/hard combat" and "ample/average/little loot". This way, players can choose how challenging they want each aspect of the game to be. And it allows more diversity than just one general difficulty setting: You could do a run with hard combat and ample loot, then one with average combat and little loot to face another kind of challenge. It would add replay value.
