Hello,
First of all, I want to understand if you have errors while running Sen2Cor 2.8.0 from SNAP Menu or if you don’t manage to run it at all. Please describe the behavior.
Second, the issue with SPACECRAFT_NAME is not related with SNAP plugin adapter itself, from the discussions in the past I remember it was caused by a GIPP file misconfiguration.
(the error is very general and usually not telling the real cause)
There are newer versions of Sen2Cor, last version is 2.10
Maybe using a newer version will solve the problem, like @Jan indicated here:
The same issue and solution was here New REFINED L1C tiles do not process with Sen2Cor 2.8
Running Sen2Cor280 in SNAP 8, without changing the parameters, it works without any issues. But I am not a Sen2Cor developer, nor user (just the SNAP integrator 
)
Maybe @Jan knows more about specific GIPP files configuration for Sen2Cor 2.8 or about this SPACECRAFT_NAME issue.