After thinking about this some more I came up with a new tail design.
My design uses a standard split ring, hangs centrally, tailstands well, includes a magnet and shouldn't add any manufacturing complexity or cost.
Here is a visualization of my idea (please excuse my terrible photo editing skills):
The area enclosed in black should all be the same height as the central lug. This should make it tailstand fairly well (not as good as a completely flat bottom, but definitely better than the three spoke design of the E01) and the split ring can freely move from a central position to one side. The tailstand area can be increased if a slightly larger split ring is used. The Olight i3E in the picture above uses a 10 mm split ring, a larger 12 mm split ring works better with the design (12 mm is also the size you'll find on medium sized Swiss Army knives).
The red dot represents the magnet. On the i3E, which has a tail diameter of 12,7 mm, a 3 x 3 mm magnet fits no problem. The tail of the jet to be named Sofirn light should have a slightly larger diameter which means a 4 x 3 mm magnet should probably be possible.
Just for comparison: a 4 x 3 mm magnet has about the same retention force as a 5 x 2 mm magnet (according to a couple of magnet shops). The stainless steel DQG Tiny AAA uses a 5 x 2 mm magnet on the inside of the light (i.e. there is a layer of steel between the magnet and the surface it is attached to), yet the magnet is strong enough to hold the light, even horizontally.
What do you all think?
Perhaps TheShadowGuy could include my design in the survey?