I like both options. The only flaw is when an op isn't on and is too late, but perhaps a message could be sent to an op on IRC [e.g "Someone is reporting grief! Do you want to stop the timer? y/n] so if he/she says y the timer could be stopped for the op to get on.
Not sure how hard that would be to code onto IRC (I'm sure it'd be manageable in-game), and a flaw with that is if that Operator isn't voiced (most ops are auto-voiced, which means they're automatically given the privilege to talk on IRC, but on default you aren't allowed to talk unless someone voices you. New Operators need to be voiced as they're not voiced on default).
Ops/Vetops should have a command to pause the round timer, if not the lava timer. I have seen 3-4 times lately that a grief was unresolved because the round ended before the ops could get to the grief in time. I believe that such a command could only help.
There could be some options added to the /vote command for this. For example, if you do /vote @@1 it would start a vote for the round to end, and depending on the votes it'd end the round. We could have one called /vote @@3 which would start a vote to pause the timer for 3 minutes. VetOps would get the actual command to pause it, while Ops have to use a vote. The problem with this is that the staff could abuse it to stop the round forever or VetOps could forget to unpause the round if they have to leave really soon after that, causing the round to be stuck forever. This'd be useful, but I think pausing it for 3 minutes would be good enough, and a rule to staff to only use this for emergencies or when you're investigating grief near the end of the round.
I support this, but I don't believe this is a huge problem and we could well do without it, though it'd make staffing in some areas a bit easier if we didn't have time to investigate a grief. I'm not entirely sure if this is code-able, but it's worth a test in the least.
