I figured I'd start a thread specific to this issue, rather than clogging up the Aijmod thread with more posts.
Basically, I managed to get HEW running and have cloned the Aijmod-final_2003 repo from github.
I can successfully build the default rom (AZ1g202G) with the current patch successfully, but i can't get it to compile with any changes i make within the code - it just keeps building the same file (confirmed it's building a new file, but it's identical to previously built ones).
Not sure if there's a script or setting I'm missing, but it's driving me crazy and the coding guy at work is away this week so don't have to him to waste some work time with talking about it.
I'm trying to change a process in progmode.c from using the test mode connectors to using a combination of brake+clutch+cruise to enter progrmode, but it doesn't matter what code i enter (even dummy code to force a bytes change) nothing is getting included when building.
It's also incredibly hard to find specific support online as this seems to be a niche use case as well.
Any help is appreciated

Edit to add that this might end becoming more of a log of my learnings as RR isn't quite the hive of activity it used to be, but at least this way it will be documented and might be able to help someone else learn about it in the future.