Of course, the SK68 is zoomable, you didn’t specify a size, as far as I can see. In 18650 size, there are SK98 or scaled up SK68 clones, like the Raysoon TD-398 Review: Raysoon TD-398 (XM-L T6 | 18650). These have good cooling, except that the one linked above has a hollow pill, unlike a Sipik SK68.
I am planning my first emitter swap to be a large lensed SK68 clone three mode.
About light loss, there is a new design, apparently intended for mass production: 3-mode Zoom AA/1450 EXPIRED ! "Black" $1.99 Max 3ea. It is way dimmer than an SK68, with maybe 80% or 90% of the current, because it is slim and the lens has a long focal length. I put together a Fresnel lens light that has less loss because it has a higher size to focal length ratio.