Hybrids are always an unknown entity, and when the parents are from two different families the outcome is even more uncertain. Too often the result is the worst attributes of both so it is good to find plants that take the best attributes instead.
This sedum / echeveria hybrid, sedevaria letizia, must rank as one of my favourite plants: it ticks so many boxes. It's a pretty plant and while it does form trunks these are easily controlled. It offsets nicely forming either small clusters, or nicely branched "trees". It flowers well, with almost pure white flowers. Finally it is cold tolerant and with rain protection gets through our winters without problems.
I have a few of these ready for planting out when there is a dry bed to put them in. The plant above is my favourite, I can't help but think it would make a spectacular bonsai plant. Wouldn't it look amazing clinging to the side of a rock, with its roots hanging down into the soil below. It does form aerial roots, which seem stable, so it should be possible. I just have to be brave enough to to risk the pant.