1. ClrMame can scan anything
2. ClrMame does not recognize the packed datatrack either, because it was reduced to ECM-format before packing it with 7z.
3. You can use unpackiso to restore the previous uncompressed binary files. Those files are in the database and in the dat-file and thus are recognized by ClrMame.
There could be another dat file that would contain the ecm'd and ape'd format. But that would require too much work. In fact i consider packiso to not be the best thing to use, as it does not use optimal settings (ape encoder with slower insane setting could reduce audio track data by another 5-10MB and optimized 7z settings could reduce in further compression too, without being too memory intensive. A 32MB dictionary requires 372MB of memory for packing, which means every computer with 1GB of RAM can handle that. Also one could use the advanced options which would make the process slower but the compression better. Equally on all computers out there.)