Ok ok I know that you say that hl2 can't be used to play this mod but can you use halflife source? The graphics of the models seem too good for just the original halflife. So this is why I am asking this.
HL source is run on the HL2 engine. HL is run on the HL engine. ESF is coded for the HL engine. Making it impossible to put ESF on HL2/HL Source, unless they started recoding things. It's logical if you think about it.