The first thing that comes to mind is Mach3. Due to it being unsupported I’d seriously would consider another solution. Thankfully there are many solutions these days.
I’m by far no expert in large wood working spindles but isn’t 10 HP a bit of an over match for a 3/4” cutter doing 1/2” deep slots?
We don’t have a lot of details here but RAPIDS are very important on large machines. This especially if you want to machine a feature at one end, one in the middle and one at the end. Slow rapids will destroy your cycle times. Again it depends upon what you are doing but for commercial use I’d be focused on good rapid performance.
As for servos you might actually be better off with servos. When you have such a high horse power spindle you need to consider reaction forces in machining and maybe more importantly in a crash that might put far more energy into the system than normal cutting. Most of the machines built here are in the 2HP range so you have to consider thAt the common approach seen here might not fit your needs.
In the same sense a 10 HP spindle really requires a more substantial frame than the common builds here. I’d go so far as to say don’t do it unless you have well developed fabrication skills. Well skills and a machine shop. The high Z clearance for example requires a bit of thought in the design.
You will likely need rack and pinion for your long axis. You don’t need to make every axis rack and pinion though.
As for table selection generally on large machine people go the moving gantry route to save space. However for large timber handling a moving table might be a safer option. Why? Easier loading without the back breaking error to get the timber under the gantry in a moving gantry solution. There are options though, you could do a moving gantry machine with a longer travel than needed to provide a gantry parking space. The goal is to be able to drop the timber in place with a minimal of shifting of the wood required. So if you intend to do 12 foot long beams, being able to drop them directly onto the table is a big deal.
I mention the above based on experience one place I worked that Had a very larger planner mill. One thing that stood out was how easy it was to load the machine up with truly heavy stuff. That could be accomplished with fork lift or overhead crane. Now I don’t expect your timbers to be that heavy but they are heavy enough to cause injury. Side sign in the ability to load the machine easily.