to translate its potential ADSB IN then requires another firm's offerings
Well, yes, SE2 doesn't have a display, but moving map software on a tablet etc. is so ubiquitous and useful in its own right that requiring a user to have such a device to view ADS-B in from SE2 is hardly a big ask.
It needs a minimum of three or more separate components, plus wires and blue tooth etc. - all for obtaining a DIY fledgling EC scheme.
ADS-B IN/OUT with SE2 really only requires one extra component: a moving map device with wifi, which a lot of people (probably a majority) will have already. A very useful addition (some would say essential) is a Bluetooth headset or intercom. This setup has no wires anywhere, which is to me is a significant attraction over PAW-Rosetta. I bought a PilotAware unit at the time SkyEcho could not be used at the same time as a transponder, and therefore use was of doubtful legality in a transponder equipped aircraft. However, given the moves to standardise on ADS-B, I think PAW's hour has passed, and I really cannot fathom why it is on the rebate list.