Yeah, I'm not going to debate theology with you. Of course Theravadins would say exactly what you said. And I admit that this interpretation is my own. However if you read the Anthill Sutta we find a deva reborn in a god realm (not actually a Pure Land realm) who nonetheless follows the teachings of the Buddha, appears to a monk (they were friends before the dewa died in the previous life), and gives him a riddle. he monk takes the riddle to the Buddha how then provides and explanation. This becomes the object of the monks meditation who then later attains some degree of realization.
Any Buddhist doctrines, if interpret broad enough or the concept sketch far enough, can be found in any verses or even worldly teachings. Therefore its not unusual that you will choose this way of thinking which is pretty common among Zen practitioners. Neither will I fault you for it, not to worry.
On the other hand, I'm preferred to think in another way. It has been shown that Mahayana Sutras have close links with Agama Sutras, therefore some primitive or early form of Pure Land concepts might be found there. Also Pure Land doctrine was first stated in Prajnaparamita Sutras that was taken from the Naga realms and had a divine origin like a terma and was originally not of this world. For those who have problems with the first possibility and second less scholarly interpretation will seem more feasible or acceptable.
You can read the sutta according to doctrines or you can read the sutta according to spiritual purpose. And in fact doctrines at one time were or are a distillation of spiritual purpose and serve as a guidepost.
The idea that many Mahayana doctrines can be found in nascent form in the Pali suttas is one rejected by all (or almost all) Theravadin's and many Mahayanists. It doesn't bother me. Of course you have to be careful with that. Bahai's for example very much read what they want to into the suttas and sutras. I'm not doing that.
The problem with many Mahayanists nowadays is that they are quick to disregard the viewpoint of other schools like Theravada, then give them labels, call them names or much worse, telling them that they are ignorant of "hidden teachings or interpretations" that is kept within their own canon and therefore they must, in the end, conform to Mahayana superior doctrines. As a result of this, its not surprisingly that the resultant backlash coming from Theravada in the recent decades against Mahayana were pretty harsh. Sad to say, many innocent parties are caught in the crossfire and lots of bad karma produce.
If one bother to understand Theravada teachings, it can easily see that while Mahayana teachings of Sunyata allows all myriad conventional forms of material possibilities, including Pure Lands or Buddha fields, the Theravada teaching on anatta clearly doesn't. Since in their POV, material dhammas are not as dependent on one's kamma as in Mahayana. To sum up, for them, the meditating on anatta could only alter one's perceptions of the material phenomena, not changing their physical natures, laws or processes, hence Theravadins believe their universe to be a single great trichiliocosm, not a multiverse filled with infinite Buddha fields.
I respect their viewpoint and because of my great faith in Mahayana teachings, I don't see the need to constantly enforce the standard Mahayana protocol that "all Mahayana teachings have their seeds in Pali canon where they are not elaborated by the sravakas".