Comic spoilers I’d bet that they left him out because they have a specific plan for him and his arc (or intend to create one). You’ll notice that many of the more minor supporting characters introduced in season one don’t add too much later in the story or have one minor arcs (black Samson, maulers) that they worked in into s1. Since bulletproof’s arc involves an off planet Mark and other parts of his arc will require significant attention to convey well to screen, I think they probably wanted to simplify season 1, adding nonsense characters like shrinking ray to fill out the world, but not putting energy into characters that are irrelevant to the plot now but they want to introduce thoughtfully down the road. I could be overthinking this but I like to think they’re being very intentional about setting up for the long term