In Soldat, when using the Barrett for example, that blending acts as a tactical advantage. In this, I am trying to make the characters more visible, while give them the chance to use cover. While in hindsight it is a terrible design decision, the thinner walls can be used for cover, but you can walk through them at any time (provided an enemy isn't taking cover behind it).
At this point I'm finding the style of the game and the weapons involved aren't probably suited to such gameplay, especially in this map where the cover is really only centred in the bases (poor level design on my part). However, I am set on the idea of using cover in a 2D plane, but I'm just thinking perhaps this isnt the right project to attempt it on.
Tangents aside, I think you may have a valid point about their congruency with their surroundings. I initially thought the outlines would help improve readability, but it may not be needed in the end.
I'll report back to this shortly, hopefully with the beginnings of a new level and a fresh start.