Well, the Advent capital ships are actually real English words... and I believe there was a post a while back that the TEC capital ships are real Russian words, so we should be able to agree on pronunciation for these units.
Now, for the Vasari capital ships, as well as many of the units for all factions, that gets a little more tricky. The Vasari shipe names are entirely made up, and our only real angle to work on is the in-game Vasari accent, which tends to accentuate the the S and A sounds.
As far as Javelis goes, I think the root word is "Javalin" (which would make sense for a missile cruiser) and it should be pronounced as such, but that's really just an educated guess.
Jarrasul
The double R tells us that the a's are likely short, but that still leaves the U and the J ambiguous, as well as giving us little direction as to where to put emphasis. However the Vasari affinity for "S" sounds, the last syllable is the most likely candidate for emphasis. However, we don't know the sound the U makes. It might be like "pull" or "pool". Similarly, the first syllable might be "jar", "yar", or even "zshar", since J is a very ambiguous letter in the English language.
I'd go with "Jar - ra - sool" or "Jar - ra - sull" personally, with emphasis on the last syllable.
Vulkoras
The first syllable has the same problem as the Jarrasul's last syllable. It may be "vool" or "vull", and there is really no idication either way. Thematically it seems similar to a Vulture, picking on weak defenseless planets, so I'd be inclined to pronounce it that way. The second syllable could also be pronounced two different ways, either "core" or "coor". The last syllable is pretty obvious given the Vasari accent: "ass".
I'd go with "Vull - core - ass", with emphasis on the first and last syllables.
Skirantra
I'd say this is probably the most definitive of the Vasari capital ships. Putting emphasis on the S at the start, I can only come up with one convincing way to pronounce it:
"Skier - an - tra", with an obligatory long S and emphasis on the first syllable as part of the Vasari accent.
Kortul
The first syllable is pretty unambiguous: "core". The second syllable could be pronounced "tool", "tull", or "tyule". I'd personally go with "tool" based on the way it's spelt.
"Core - tool", probalby with an emphasis on the second syllable.
Antorak
I think this is probably as close to unambiguous as we can get:
"An - tore - ack", though where the emphasis goes is anyone's guess.
