So why not have low priority outbound connections or something like that(basically any outbound connections above 8 are marked as low priority)? These could be connections that nodes will drop if regular priority incoming connections are competing for space. That could be a way to implement this responsibly so that low priority connections only use excess slots and won't compete for space with regular priority connections.
The next flag you'd ask for is for a configurable option to override the low priority status...
So you think it's better to just ignore the issue and hope people don't modify the source?