Interior doors/Glass above head?

Hi, ive replaced interior doors before with glass above the head, mostly upstairs in houses. Now Ive always just replaced the frame, glass etc.

I have a client who has seven doors like this and wants to block them up, ie. fit new door and frame and just slab and plaster above. Now the problem is two of the rooms dont have vents and these rooms have a 1 inch gap between the top of the glass and the frame obviously to stop carbon monoxide build up. There is no natural light on the landing apart from these windows and I told him it may be leave the landing very dark.

Ive suggested boring new vents in the two rooms(its only a double 100mm leaf) so it shouldnt be a problem. Now as far as bringing light into the landing ive suggested glass blocks instead of blocking the glass or a skylight.

The question is firstly am i able(by law) to block these glass opes up. And secondly is there a better way to bring non artificial light in if I do.

Cheers in advance;)