How hard can this be?

90% of this part will be feasible.
Assuming the bores are the main functional feature of your part, let's look at drilling the holes for the axes first.

You'd need to flip the part four times, but even then the depth of the drilled holes compared to their diameter would require a long drill. For best dimensional accuracy (especially in terms of parallelism), the holes should be drilled from one side, and depending on your requirements, then reamed to their functional diameter.

Could you fix the part to the machine table with the thin side up?
Would you get a drill in the correct diameter long enough?
Will the drill in the spindle fit above the work piece in its entire length including some gap? Think Z height and travel.

Thank you Bodo. I'm thinking of creating 10 at a time so I will need to cut the front and back profiles first, then, using a contoured jig set them in a vice and drill/bore the pin points. Not sure where to get good drill bits of that length required. Hoping that the bit will not be so long that it interferes with the total travel Z.

What speeds and feed rate would be ballpark for milling the part? It's approx 100mm across. 9mm thick bracing.

Let me clarify - what are the dimension a and b, and what's the radial tolerance between both the orange axes?

Dimension a is 70mm, b is 5mm dia. and the tolerance I'd like to achieve is < 0.3mm

A 5mm drill with more than 70mm drilling depth should be obtainable. Coming back to the thread title, I borrowed a picture from Stoney http://stoneycnc.co.uk/stepcraft-cnc-videos/ , which shows an SC with spindle and tool fitted.

(Stoney, I hope you don't mind that I've borrowed your picture.)

To drill a 70mm deep hole into your part on the SC, you'd need to make sure that the distance 0 to 1 is high enough to let you drive your drill through the part into the sacrificial plate, so that the drill tip dives in completely in order to have the full 5mm diameter throughout the hole; and an air gap between drill and part, in order to avoid scratches.

If 0 to 1 is high enough is also influenced by 1 to 2 (min 70mm + tip), 2 to 3 (depends on the spindle you've chosen).

Alternatively, you could mill the part's contour and the wave shape, and just drill two pilot holes with a short bit; and then take the part to a drill press, and finish the deep holes.