That's one side of it, you want a system that plays to their strengths, and minimises their weaknesses.
A system that requires a fast player to bail you out frequently by using their speed, isn't necessarily playing to that strength, just taking advantage of it.
We've no way of replacing VDV's speed when he's unavailable, which unfortunately has been quite frequently. In that sense, making his speed an integral part of the desired system, as opposed to a bonus only required from time to time, isn't ideal.
Whilst you can draw parallels to Walker in his time at City, they were so dominant across the whole field that I don't think he was called into action as frequently as VDV for us.
As for the second bolded part, no, not for me. There's no way it makes sense to make it a feature of your system that a cb should routinely be having to hare back towards his own goal in chase of an opposition attacker. It's too much strain on the player, and there's no guarantee that once he gets back he'll definitely snuff out the attack anyway, see Newcastle away last season for an example of him being put on his arse.
The high line risk vs reward for us simply does not provide enough reward, our attacking players aren't good enough or smart enough to consistently score enough to outweigh the goals we gift away.