The most of R1a could indeed be similar to R1a found among West Slavs. After all it is known that Eastern Alps were settled by Slavs from Northeast.
I2a (that is probably I2a1b1a) should be of mostly the same origin to I2a found among South Slavs.
R1b is probably most numerous pre-Slavic haplogroup and I would also relate it it to Celts.
I1 has frequency of around 10% and good part of it could have been brought by Langobards.
There are also E-V13 and J2 in smaller frequencies (probably mostly of pre migration period origin).
So I think it is not wrong if we say Slovenians are all that: West-Slavic, South-Slavic and Celtic, but also there were other people who had chosen today's Slovenia to settle there.