It’s a nice idea. I agree with @WoWi that it should be a very rare sort of thing with all kinds of limits. That includes also a time limit which is the most charming aspect of attacking a titan. For me at least. We try to squeeze in as many tiles as possible while keeping our heroes alive. This creates excitement which would be gone if such a ticket won’t have a time limit.
Perhaps a ticket which expands the time limit to, let’s say, 5 minutes.
I can see myself using such a ticket when the titan has 100k HP left, we have 10 minutes of the battle remaining and my other alliance members don’t have any titan energy left to spend. Especially useful for the less active alliances and the alliances with a mixed strength of players.