Separating a black & white image for multiple colored garments

[Wildcard]

Hi all,
I'm looking for some advice on what I expected to be a simple separation job, but has now got me stuck (and this should probably be relocated to the noob section). How would you sep a simple photo image to work as a 2 color print on both light and dark color garments (with the bare minimum screen count)? I have attached an example image similar to what I'm thinking of: some solid type and a photo, where the print image would be fairly crude/stylized with halftones of 30lpi or less.

Its not as simple as I initially thought to get a 2 color image to work across all base colors, but I could be approaching the issue from the wrong angle. Now I'm thinking it will be easier to just do 2 separate single color prints, one for light tees and one for dark.
Any thoughts or recommendations?

[Dottonedan]

What color inks?  Also, not sure how you are trying to approach this.  Is the background knocked out showing the shirt outside the head and type....or is background printing like a rectangle?

[Wildcard]

I had imagined it having the base colour showing through as part of the image tones, no outer rectangle, but that was when it started as a 1 colour print on lights only. Now that dark tees have been added to the order I'm wondering how to rework the design.

I am doing the art and have freedom to play around with it, but this also means my question is open-ended... just throwing the net out for some different approaches to making a 1-2 colour photo image work over a range of base colours.

[Dottonedan]

Most of it would rely on the underbase filling in a lot of shirt color...but the top color needs to form some shape so you would need a decent amount of halftones in the top color also.

[Wildcard]

Thanks Dan, I think where I was going wrong was trying to let the shirt show through in the mid tones. But that looks all wrong when the shirt colour changes too much. Your images make sense.