From my understanding, the T'an T'ui set was special choreographed with unique movements from other schools. Only Jingwu will have this 12 routines of T'an T'ui. You can't even find this set from the original T'an T'ui school in Shantung.
I actually did hear than my school's lineage is primarily influenced by Long fist styles from Shantung.
Thus, the teaching curriculum within the Jingwu varies from centre-to-centre. If you are looking to learn a un-mixed style, then schools like Liu-He-M'en, Da-sheng Piqua M'en, or the 7-star praying mantis will meet your expectation. Da-sheng piqua M'en is a Northern monkey style.
Thanks for the recommendation, but I have decided to stick with my current instructor for now. Many chinese martial artists throughout history picked up and adapted combat techniques for their own benefits. I don't think styles need to be "pure" or have "unbroken lineages" - they just need to be practical and applicable to one's own philosophy. After all, chinese martial arts are very practical. In terms of practicality and effectiveness, I think both mixed and un-mixed styles of traditional kung fu are all on equal levels. Not so sure about this recent movement on trying to turn kung fu into basic kickboxing and wrestling, though.
We seriously need more discussion about Northern Long fist styles on this forum. They're very much neglected compared to other styles like typical IMA styles or Southern kung fu styles.