Is it possible to assign EPS or AI vector patterns directly as texture swatches?

If they are vector patterns you would see them as pattern swatches in the Swatches panel of the .ai or .eps file.

If they are not in the Swatches panel you need to add them one by one, either by dragging them with a no stroke/no fill rectangle behind them or by selecting the "pattern" object and using Object > Pattern > Make

Once you have added them all to the Swatches panel, save as an .ai file.

Open your Print.ai file and select your swatches file from the Swatches panel menu > Other Library.

Select all your swatches in that library panel and choose > Add to Swatches.

White patterns will not be visible, so leave them black.

When you use a black pattern on an object, choose Edit > Edit Colors > Invert Colors to make them white.

Can you clarify your question: Are you talking about vector patterns you're acquiring in AI or EPS formats? Or are you talking about vector patterns created by Illustrator via its Object > Pattern > Make feature. When you create a pattern or edit one using the latter feature, patterns are automatically saved as swatches.