There are actually a lot of consequences to cheating?
In DAO, cheating will get you called out by all of the love interests. Some of them can be lied to for a little while, but eventually they will all ask you to choose between them and the other(s) - if they won't straight up break up with you and tell you to go enjoy your side game. Yes, you can exploit broken mechanics to end the game with more than one romance flag activated, but that's not supported by the game's storytelling itself. As far as the romances were written, you had to make a choice at some point, and suffer the massive approval loss on whichever part you decided to let go/whichever part decided to let go of you.
Personally, I wouldn't call being forced to chose between the two people "consequences" (I haven't done all the possible combinations, but those I have done all came down to you chosing which to continue and nothing more other than a small reputation hit with the other). You get still get the benefits of romance with one and a quick shag with the other. Consequences would be something like both of them refusing refusing to continue their romance with you - your original partner dumps you flat out for cheating without even giving you the chance to explain, then you try to hook up with your bit on the side who rejects your attempts at a serious relationship by saying it was just a one night stand that they have no intention of expanding upon.
Not that that's going to happen - the romances in Bioware games, while usually rather fun, are always more about satisfying player's fanatsies than actually trying to be believeable relationships with people who actually have agency of their own. You might ultimately be limited to one person, but if the player wants to romance one of the options, they pretty much always get to...