I'm digging up an old post, but Google led me here as I was trying to replace DOSBox with DOSBox-X. LaunchBox 11.8 is still using the single quote syntax, e.g. -c "MOUNT C 'D:\MS-DOS\SR2'" instead of the -c "MOUNT C \"D:\MS-DOS\SR2\""
The latter syntax works with DOSBox 0.74 as well as DOSBox-X (I tested both). Could you please fix this in LaunchBox?