This is from the Full Briefing and I'd stick by it:
..."Specifically
Only those German land and air units belonging to the 'Panzer Group Afrika' formation (sandy coloured for easy identification) may be moved by sea to North Africa and the Middle East, or be used to sea assault Mediterranean islands. German airborne/marine units may also assault the islands. If the islands are captured, regular German units may be shipped or flown to them to act as garrisons. Only one panzer corps ('Deutsche Afrika Korps') plus an HQ and some air units will be available initially, once Italy enters the war. Other 'Afrika' units will appear following the capture of the Mediterranean islands and ports, representing the improvement in supply and shipping range that would have resulted. Malta = one panzergrenadier corps and a motorised flak division; Gibraltar = one panzer corps; Crete = one motorised division; Cyprus = one motorised and one engineer division; and Alexandria = one infantry corps. They may also be used in Continental Europe if required.
The above restrictions don't apply to Germany's satellites and allies in the Mediterranean (see below), nor to regular German units which are able to move via Turkey into North Africa and the Middle East."
Capturing the various islands and ports listed above unlocks the various PGA units for use in North Africa, representing the benefit from the additional shipping/supplies/strategic ports/improved Italian cooperation, etc., that are considered to be supplying these extra units. The Axis player may still not ship standard German units. Remember that no such restriction applies to Gemany allies/satellites in the Mediterranean, principally the Italians. We found that allowing standard German units to move to the area just results in an enormous and unhistorical build-up, followed by the swamping of the Commonwealth forces there. An - in fact the only - alternative is for standard German forces to fight their way through Turkey (this risks triggering the USSR's TO to DoW Germany) and then down through the Levant. This is quite difficult given the size of the Turkish army, the difficult terrain, and potential Commonwealth and Soviet assistance. The supply situation would still have been very difficult, but I suppose that we're envisaging regular engineers and railway troops, the Organisation Todt and hapless forced Turkish labour improving the roads and railways behind the lines.
We had some very lengthy debates on this issue, and the abovementioned compromise was generally felt to be the most 'alternatively historical'.
If you really don't like it it's best to negotiate with your opponent first.