If they did that, the bulbs would melt.
Please do not mess about with your headlight circuit, unless you know what you are doing. Sadly, you have demonstrated rather well that you don't. In particular, you MUST NOT introduce any single point failure mechanisms, other than those which are already there, and that means that you can't add fuses unless you fully understand what you are doing. The headlights both going out suddenly in a dark, twisty road is likely to be the last thing that you are ever aware of, and irrational messing about is a good way of making that happen.
Have you told your insurance company of your bodging, which most certainly has increased the risk?
Oh dear. This forum would shut down if bodgers had to notify their bodges to their insurers. Just read about some of the lashed together rust buckets that people drive around in.
Are you seriously trying to tell me that the Mini electrical system was ever designed with some element of failsafe and redundancy in mind? As an engineer dealing with fully redundancy control systems, system that will swap processors and I/O in 1 cycle in the event of a failure, I also kind of understand the way things should be done - the Mini lighting system is laughable in it's naivety and I think your a little bit out of gear picking on our friend, who may well know quite a bit more about systems than you give him credit for.
Oh, and 55/50W with both filaments running together won't melt the envelope, it may well melt the lampholder, but it won't melt the glass. Try it.
Ahhh - a fellow I.T. professional. Yes, redundancy is key in my line of work to - right up to DR and hot swapping. It's not uncommon to have 3 or even 4th level redundancy. The wiring in a normal memory is a joke - however it's basically an evolved loom from 1959 where things like 'safety' where an optional extra that wasn't available.
How many times has a mini had a 'stroke' (i.e. the lighting on one side decides to pack up, and then mysteriously work fine again the next day).
And 5 fuses in a plastic matchbox under the hinge of the bonnet? Great idea!
Thanks for your words - it actually makes a difference when someone criticises or compliments attempts at improving things. It can change a person's feeling from 'I can't be bothered' to 'I'll get this sorted' or vice versa.
Forums like this can be so helpful when someone comes up with replies like KernowCooper's which addressed my issue directly.
KC: if you have the colour coding for all the switches that would be great for the records!!
Control systems engineer amongst other things 
Mostly Siemens and AB Rockwell systems when it comes to hot swapping.
Oh yes and for good measure they sling a few more behind the dash in some models, just to make life interesting.
