How high is the tub container wall from the floor? How are you getting in the tub now? What ever you decide upon, you need a non-skid surface for your safety.
You don't want steps like on a deck or off a back porch area, that would not look good in the MBath. Do you have any natural wood trim in the room?
Thinking on this I would suggest what I call a running step. I would think that you would want a step all along the front of the tub so that there is NO one way to enter, you could enter and exit all along the tub front.
This is actually a series of two seperate rectangle boxes. The first box could be the total length of the front tub, then lets say 2 feet wide and 7 or 8 inches high. The second box would again be the length of the tub, but only one foot wide and 7 or 8 inches high. This would allow for an extra wide tread and a 7 or 8 inch riser. Now attach the top box to the second or base step.
The material could be a very pretty oak 1 x 6's or even 1 inch oak ply. Then you could stain this a complimentary stain to match the colors in the MBath. Then seal the wood with a satin polyurethane finish. Apply two coats. When thoroughly dry, apply a adhesive backed non skid strip all along the front or nose of each step.
I think that this would look good, become practical, and also safe. If you do not like the idea of staining then you could paint it. If you paint it I would definately NOT use oak, consider pine or birch.
Also, I forgot, caulk this very well as water will be a factor on the step and you want to deter rotting.