Again, there is nothing wrong with modeling the corners, it simply wasn't the question he was asking to solve. So popping in and saying "more geo" but ignoring his actual problem wasn't very useful.
Also, i'm not sure about you guys, but to round the corners on a mesh like this on the low it takes two clicks, you literally do it in just a few seconds:
Depending on how complex your curve is in the high, you may need to adjust to account for the "shrinking" of the sub-d mesh, so you can't always just take your cage and optimize it, it would likely be off a bit unless you had a lot of sides to the curve. So then you're tweaking the curve after the fact and that takes more time than just quickly recreating in the low.
There is more to think about sometimes, IMO in this case the absolutely fastest thing to do is model like I did, then take the 2 seconds to bevel/chamfer the corners in the low, really simple, really clean, really fast.
With a more complex asset I would probably do something different, but there's no need to out-think yourself for something like this.
RE: the little man: Unless you're going to have a glass pane modeled with alpha there on top of it, there is no reason to model in the depth here. You wouldn't want that normal detail if you were trying to mimick the reflective properties of the glass/plastic pane that is on top of it.