Correct me if I'm wrong, but wouldn't replacing the sleeves require hot-pressing out the old sleeves and hot-pressing in the new sleeves? Doesn't sound like a in-the-garage process.
Why would pinning be a waste of time? Are you saying the pin does not prevent slippage?
Liner slipping is not really an issue with these engines. It was a problem in older blocks.. the 3.9 and before IIRC. The 4.0/4.6 has improved seats at the bottom of the bore so the liner can't move downwards. I think I read this in the "How to power tune rover v8 engines" book
The real problem with these 4.0/4.6 blocks is getting too hot, and causing the already thin water jacket walls between the bores to crack, allowing coolant into the crankcase and into the combustion changer. The flanged liner, with o-rings at the bottom, theoretically allow a cracked block to continue working just fine, as the flanged lip at the top prevents coolant getting past the head gasket, and the o-ring at the bottom prevents it going into the crankcase. There are other benefits but I can't remember them off the top of my head
Anyway, not a DIY job. You can mail your block to Q&E in LA, and they will put the liners in for you, for $1500.