I would like to see some of the 'missing' items to consolidate the Israeli and South African lines, such as the Magach 6 with ERA (1982 Lebanon vintage) and the centurion similarly equipped. The Sherman 160mm mortar would be cool,as well. Not sure how the '48 modified armoured cars would go, but they'd look very cool.
South Africa could do with a Rooikat 8x8 to accompany the horde of Ratels, and the Ratel ATGM variant would,cap the collection off quite well. There's also the 106 RCL and 81mm mortar variants of the Casspir to consider (the Casspir is one of the outstanding miniatures I've picked up,lately - it paints up fantastically & looks very impressive).
I'll second the wish for the Patria AMV, since it's got a lot of production in several variants.
One of the glaring early Cold War gaps are the heavy tanks from the U.S. And UK, namely the M103 and Conquerer. These would pretty much finish off any required tank fleet from that period. A ferret with ATGM would be excellent as well.....
Aircraft-wise, I'd like to see a Hawker Hunter & Buccaneer for the same period, and the Sepecat Jaguar & Falklands Harriers (Sea Harrier & also the RAF GR3 version).
And how about a plain-Jane Huey-Cobra for Vietnam ??
Someone else earlier suggested an open top version of the Canadian C15 armoured truck, which would give me a plausible excuse to by half a dozen more packs of them....
I'm sure I've missed some glaringly obvious 'must-haves', but these should be a good start....