Quite an enjoyable read.
On the Full FU option, I must say I loved the original three series from the UK and just how manipulative old Francis was, that aside something similar could have been achieved without conscription.
Options for change severely cut the size of the British army but the general staff fought tooth and nail to keep as much armour (including wheeled mech) as possible at the same time as many other nations deliberately increased the ratio of "light forces" to traditional cold war "heavy forces". Maybe the UK could have further reduced the number of regular heavy formations, maybe even moving some of the capability to the Territorial Army or even making a percentage of regular Armoured and Mechanised units reserve or composite regular/reserve, or even cadre/reserve and ploughed the remaining budget into rapidly deployable marines, airborne / airmobile and light infantry brigades with minimal light armour. Fewer job losses in the military, fewer base closures, smaller detrimental economic effect and there would still be a very substantial saving from the expensive armour and support gear laid up in reserve or disposed of.
What would these troops do? Peace keeping and HADR, which the UN pays nations to do, it was actually a significant source of income for the likes of Fiji, Nigeria, Uganda, Pakistan, Jordan etc. Not sure but it wouldn't surprise me if France, Australia, NZ and Canada were reimbursed for many of their UN deployments. Whitemans burden? hardly, more good global citizenship and I don't imagine civilians who have lost loved ones to brutal criminals and zealots would really care what nationality the people wearing the blue helmets were, so long as they were disciplined and part of the solution and not the problem. In fact in certain situations the people concerned would much rather being protected by effective, well trained and disciplined first world troops than some of the alternatives who have looked at peace keeping tours as a form of sex tourism. Besides, its been a long time since the British, or most western armies for that matter, could be called "white" or even specifically "Christian", that's the thing with multiculturism in the west, there are lots of proud British, French, Dutch, Germans, Americans, etc. etc. whose parents, grand parents, etc. were very proud some thing else.