I may have missed something, so please correct me if so, but at present I don't think there is a simple way to get a moving light to fade between two positions in a linear rather than polar behaviour.
This is something the Strand Palette could do 10 years ago (though admittedly it also excelled at blue screening mid show, which EOS is (generally) better behaved at), so doesn't seem beyond the realm of ETC's coders nor the hardware platforms of the consoles.
So feature request - linear movement - perhaps something like colour path but for focus data.