As I was researching low cost DLP solutions I found this project by sirocco where he converted his old Delta into DLP SLA 3d printer by putting a projector on the top opening and adding vat resin. Delta configuration looks like good option due to hight.
I'm not sure how he moves his vat with salt water and resin, it could be done by separate mechanism or by some type of vat tray mounted on three points to the Delta frame and moved by existing motors.
Source, more details, but no clear instructions:
Print results look decent: