When fire damage occurs, it occurs in layers. Maybe something like light, medium, heavy, and husk. Each layer requiring both time, tools, and a skill check to strip off. Tools required to be present could be things like mop buckets, shovels, wrecking bars… Heck maybe even have a special repair item in the form of construction materials be sold at the construction yard for that really heavy damage done.
I also think that any services that the room has should be rendered inoperable until the fire damage has been repaired. While this may be as simple as spending two minutes mopping up, it is an actual impediment to a gathering. Furthermore I think that if ambient fire damage hits too high a level that a room would essentially "husk out" and destroy the entire room description. This obviously wouldn't happen with every little fire, but could stand as a legitimate goal for arsonists to shut down a location for an extended period of time.
As for the time gates to repairs, have them be arcadey at one end, but realistic at the other. A molotov immediately stomped out could be a five minute cleanup of a couple of people getting brooms and whatnot. Maybe you have to close down for an hour to really clean up. But if Napalm Nathan walks in with his flamethrower, it may take up to like ten to twenty hours of work to undo his chaos. Multiple people can chip in their time obviously but making repairing a location a group effort requiring significant hours of investing in being in a single location for extended periods of time would probably foster a LOT of roleplay.
But yeah, a molotov thrown into the party warranting more concern for clothing than actual damage is a thing.
A timer could help with that, sure; But people could also Roleplay.
Just because sindome is classed as a 'game' doesn't mean that we must treat everything that has a command on it as the thing to do.
If we see fire damage, why not use your own Roleplay common sense brain and do some .roleplay on tidying up the damage for a bit before we use the roleplay object's command to make it vanish, why not call in WCS to deal with it so they can get roleplay (Even though you can do it, we wonna spread Roleplay out, right?). Make a scene out of it, don't just rush to commands because they're there.
But alas, yes. Game mechanic shiny and timer would help it take longer.
I like idea of impeding a gathering and rendering services inoperable, it's interesting and forces the issue! However…I disagree with the room description? Because getting to dictate when a room gets husked out seems much more along the lines of an RP consequence than a fact of life - these places have been hit before, and are built to outlive the inhabitants is the feel I get.