I think raw data e.g. SNPs, STRs should be attached as media objects instead of adding all that information into Gramps.
- Person relationship to DNA company: I use person events for that (event type: DNA test, date: date of the test, description: kit number or username, place: name of the company)
- Y-DNA data: Also a DNA test event and my YFull kit number in event description. The 780(!) STR markers are added as media file. My latest Y-subclade/haplogroup and my mt-haplogroup are added as person attributes.
- Shared cM length: I think the current system is okay, but I think it has some weaknesses: (1) no information about the testing company, (2) no information about the genome build version and (3) no way to indicate triangulation.