just wondering if there was anyway to easily customise it so we can add a refill timer and refill amount as some players are abusing it to basically change for scrap and it would be nice to at least cap this to some extent?

Did you find any config?

i was hoping dev would add an option, seems to have gone quiet on this front

I can't see the dev adding this option since the point of the plugin is to always keep the items in stock without delay. If you're looking to stop players from abusing it, i would suggest using Vending Machine Timeout.