Ok here you go by special request:
DSTWO_DSiModeLaunchers.rar
There's two here. The main version and the one that boots the plugin menu I assume. The first one boots to white screen. I don't have a DSTWO so I can't determine if that's a problem or not.
The second one boots to white screen then black screen. That one looks a bit more promising and I think it might do more if a DSTWO is inserted. For now that's all I plan to do for the DSTWO.
These launchers boot into DSi Hybrid Mode. (I found this to at least be a bit more stable then DSi Exclusive mode as a result of R4 tests in this mode).
Assuming they work at all, these are experimental. I'd advise others not to attempt to use them unless they expect to run into issues.
Also still looking for a rom dump of the Gateway Blue Cart. Wanna try and boot that in DSiMode too.