Just to followup on adding the transparent 1x1 image for srcset. By creating a python script that parses the html on export using beautifulsoup 4, I am able to search for all the images that have the class "lazyload" and add the attribute srcset="data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==".
This now gives me total design freedom inside Bootstrap Studio to see and edit freely all the images and then add the srcset on exporting my project to accomplish proper lazy loading format.