There are some old Mac apps, like the once splendid NISUS 3.06, that I like to use, via Classic, in Mac's OS 10, and so I wonder whether there is a virtualization method in FUSION to use these in the newer Intel Macs?
Nothing in Fusion, no.
Fusion (as all of VMware's products, are virtualization, not emulation, products. Meaning they virtualize n[/i] x86 or x64 machines on top of another physical x86 or x64 machine. An emulator is what you would need - a product that emulates a PowerPC chip on top of the Intel. I don't believe any such technology exists that is as robust as what Classic was... SheepShaver and PearPC seem to be loaded with caveats.