MLU on the EOS-3 and EOS-1V are as you say - embedded in the function. I never really thought of it as particularly clumsy in all the years I used it. However, now that I am immersed in pre AF cameras, I can see how adding it's own switch would make it more accessible.

Would the Nikon F be the first 35mm SLR with MLU? It is certainly the goofiest MLU implementation I know of! It has it's own control that you turn but it won't raise the mirror at this time. You have to first advance and fire the shutter once at which time the mirror stays up so that it would be in the up position for the next time you advance and fire the shutter.

The next goofiest MLU implementation I know of is the "unofficial" MLU on the Pentax MX. You advance the shutter and then "pop" the shutter release momentarily. This will raise the mirror and then after that you can just fire the shutter and the mirror would come back down as normal. This works on all of the MX's that I have owned (4) and other MX owners have also confirmed that this works the same for theirs too.

The only other goofy MLU configuration I have is on the Pentax LX. It is straightforward enough as there is a control for it. However, this same lever activates MLU when turned one way but the same lever is used for the timer release when turned the other way. This arrangement means you can't use the timer and MLU at the same time.

Otherwise, all the other bodies that I have with MLU are straight forward mechanical linkages that allows you to raise and lower the mirror at will.

But of all the MLU capable bodies I have, I find the way Nikon FA, FM/FM2/FM3, FE/FE2 and even the cheapest FG implementation to be the best even though they don't have an independent MLU control. In these bodies, MLU is automatic when using the timer.