The spindle on a horizontal machine is usually stationary in the Z axis, like a lathe. The spindle moves vertically on the the Y axis unless there's a knee involved in manual mill style.
Maybe you're aware of that but the wording makes me suspect you're not naming the axis in the conventional way.
I would also like a mini horizontal (with rotary axis) but the design I have in mind doesn't scale down nicely.
A web search of Horizontal Machining Center (HMC) will find machines stripped to their bones.