ATA’s usually do not usually provide visual message waiting indications.
Most analog telephones with message waiting lamps require an electric pulse to be generated periodically to make the lamp flash.
This can be problematic, as some phones use LED’s while others use neon lamps. Depending on which your phone may use, the power pulse must be larger or smaller. ATA’s don’t generally support such operation.
The pap2t can do visual indications using FSK, but that’s it. Your phone will have to support FSK indications as well.
I believe you will be limited to using only stutter dial tone (audible message waiting indication).