Not a big fan of the rod-eye linkages used in the trailing arm setups. OK for track, but British roads will see them wear out in no time. Going to go IRS. See you in 2011
A metal on metal type rod end would certainly wear quickly due to the lack of lubrication but a good quality rod end with a teflon liner should last a long time.
Something like a 1/2" rod end is rated to something in the region of 25,000lbs (12,000kg) static radial load. From memory Goldline specify for heavy fatigue loads in a pure tension compression situation that the bearing can take 10% of its static radial load (1,200kg). Please dont quote me on that though, its from memory not fact.
Now i haven't done the calcs yet to work out what the loads are but if a bearing can take 1,200kg in a fatigue situation i dont think something the weight of a mini (circa 700kg) is going to induce continuous loads of size that would worry it.
Dont get me wrong i respect you decision to go IRS i just think its a little over complicated/heavy for what is needed plus as you rightly say design and fabrication is somewhat time consuming lol.
On a seperate note have you thought about diff options?