Does this lath and plaster wall look safe to remove?

[OldManKensey]

I'm trying to expand our loft hatch and install some better steps. First stage was to remove a lath and plaster wall separating the cupboard where the hatch is from the bedroom.

And this is where I'm at now, that wood looks thicker than I was expecting, that framework is the darker wood in the third photo taken from inside the loft.

What's the best course of action now? I suspect this is a job better suited to a pro, even though the wife is telling me it will "probably be ok to remove it"

being bit pessimistic, if we got someone in who said that framework has some structural function, what would our options be? Plasterboard it all back over and forget the larger hatch?

 

[Wayners]

Not very wide so if timber is bridging cupboard then I can't see why you cant take support out over that door. Was that what you wanted to do?
Timbers were always bigger years ago Vs the thinner timbers seen today.
Just look at it and decide for yourself if there is going to be a problem.
If unsure get advice but a tradesmen might not want to advise so you will end up employing a structural engineer.
You also have vermiculite. Consider testing that for asbestos. Not sure what the latest thinking is but I left alone