I second Ezgoing's comments about the comfort of proper cover and secure seating. Mostly folk on ribnet make comment about how a boat looks and that appears to be the general method of assessment.
It's a fairly minor consideration for me...form before function seems to be the modern way...perhaps I'm just too old. Anyway, I think your initial idea of a three sided cabin/wheelhouse with a rear curtain for protection and warmth is a good one. A 6mtr boat can easily accommodate a structure of medium weight.
I'd take care when considering the ribs with a console and roof as you've linked to above. I ran a rib like this for a couple of seasons but it had a few disadvantages which were too unsatisfactory for me and eventually the roof was removed. (I've still got it if anyone wants a roof FOC.) The first is that there is a surprising amount of heat from the sun to keep you warm in an open boat, even in overcast weather, compared to always being in the shade under a roof. Obviously if you're in a warm climate then the shade will be an advantage but I never found it so here. Secondly, the air that may otherwise deflect above your head is trapped by the roof and you're captured in that draught between the top of the screen and the roof. Thirdly, there is considerable reflection of noise from the outboard motor reflected off the inside of the roof, enough to make a long journey wearying and I found it irritating, so much so I took to wearing ear defenders.