As to the cost you cant value you life very highly , this is very cheap TCAS/ WX radar system that will fit most light aircraft those who have fitted the Garmin 430 already have the means to display the imformation so I cant see the problem if it costs me a few quid to have traffic/wx data that at the moment is the preserve of the airliners and biz jets.
A couple of organisations are currently investigating the provision of weather data via uplink to Garmin 530/430 and similar systems. Announcements likely later this year.
TIS (the TCAS-like traffic information seen in US terminal areas) is not currently planned for the UK at all.
A and C
So there is a chance that you may get weather radar info, although I suspect it costing "a few quid" may be a tad optimistic. But with regard to collision avoidance it looks like you will have to carry on to looking out of the window.
The point being made here is that some people want to fly IFR, fly through CAS and fly around weather fronts, whilst the vast majority of recreational pilots do not.
It will be physically impossible to fit these units to the majority of microlight and permit aircraft. Under the current proposal even balloons will have to have them fitted! Whilst Permit to Fly aircraft are not the bulk of the UK private flying fleet, they are a significant part of it. When you look at hours flown, I suspect that they are the bulk.
These aircraft will not be any safer with Mode S fitted. They will, however, be ripe for taxation.
The cycling analogy misses a couple of points... You only need lights on your bike if you ride on the road
and you ride at night. For the lights on your bike to be effective, you do not require the installation of hundreds of millions of pounds worth of infrastructure, which you are likely to pay for everytime you go for a bike ride, on the road or off of it, in the dead of night or the middle of the day.