The valve blocks increases/decreases air into the strut. If there's anything obstructing the valve block to the strut, it'll affect normal functionality. So, a 1-way ball valve in between would be bad. It needs to deflate the strut too.If there were a valve in that 3 way connector, whereby it wouldn't let any air up the green line (thereby eliminating the potential for major leaks in the green line or at the valve blocks), then I would think it would affect a normally-operating suspension's ability to lower the pressure in an air spring, as I'm fairly certain the air tube is also where the air strut exhausts air pressure.
Am I right in thinking that?