Yeah last time I did this we used regexes but I really don't like that solution. I think the waiver should go in the RTL itself. I don't know why nobody does that - it's standard practice in software. SV even supports attributes exactly for this sort of thing. The tools don't support it but you could make a tool to parse the files and convert it to TCL. I've done something like that using the Rust sv-parser crate before. Tedious but not impossible.
Also we found the formal waiver analysis tools to be very effective for waiving unreachable code, in case you aren't using those.
Congrats on the silicon anyway!