Tangent Line as datum

[Bux1986]

Hi
1) Can I use the tangent line in red as my third datum?
If not then what would be the correct way?
Please see the attached picture.
Thank you

 

[Bux1986]

Thank you everyone for your valuable feedback.
I ended up using the holes as datum and profile control.

Will share the feedback, if any, from the manufacturing department.

Thank you