The freeze only occurs right when Beast Emperor shows up. If you skip those few lines, you're safe. It doesn't always happen though. It didn't happen that last time I played, and so I'd actually completely forgotten about it. I've never encountered a freeze during SN5, so it's either the ISO or the emulator you're playing with.
SN3 system data not only unlocks all the SN3 puppets from the beginning, but it also unlocks all the summon beasts SN3 and 4 have in common as well as the four student-exclusive summons (which are only available if you have SN3 system data). Of course, since only the students can get any decent mileage out of them, they only come in useful for free battles and the infinite corridor. But SN3 surprisingly fails to include one of its illustrations in the gallery. The one with the volcano is not in the gallery and therefore can only viewed in-story. There's also an unbelievably annoying infinite corridor bug, which SN4 thankfully doesn't have.
Swordcraft Story 2 should have the official localization of 派閥 since Nina is the blue one, just like Mint, but hell if I know what it is.
The difference between 竜 and 龍 pops up in SN4. Since Silturn is some weird fantasy mash-up of Japan and China from what we see, using 'long' or 'lóng' for 龍 might work (especially since the two 龍 we see in the series of Chinese-styled names: Seilong and Mei-Mei [Xiao-Mei] and Ouleng), but it gets kiiinda awkward in some lines, like when Seilong declares he's 龍人族の次期族長 when he first shows up. There's also the case of stuff like when it's pronounced 'Elgo' (officially, according to SN3, 'Erugo,' but that's just ugly) but written 'will of the world', as well as Kentarou's... uh, I forgot the way it's pronounced, but I think it was written as some variation of 'beloved'. But just including the written version as a parenthetical should be fine.
Another issue is that a lot (all? probably all) of the endings include lines that are pure audio. You'll need to include some kind of subtitle system to translate those lines. And if you're going to do that far, you might as well subtitle battle chatter as well if you've got the time; some of the lines for support skills are legitimately hilarious. You might end up having to use something like L, Sa, Si, M, N for certain screens having to do with summons. Also certain skill names, especially for battle pop-ups, might require shortening or the box lengthening.
If you want to keep the spoiler located in the main characters' default names, it's probably best to go with 'Rye' or 'Rie,' but expect bread jokes, especially since the kid's good at cooking, if you go with the former. The 越響者 class has an official localization, on the same lines as as Linker for 誓約者, Lawler for 超律者, and Saver for 抜剣者. It's クロスレイヤー, mostly likely 'Crosslayer,' as nonsensical as that is.
Apset's usage of four kanji combinations + English will probably become idioms/sayings with the English staying in all caps? Will the Loreilal kids having their uppercases and lowercases flipped to simulate the katakana/hiragana flip? It's pure favoritism on my part that makes me say 'there's no way to localize the way Corlal speaks that keeps how cute it is in Japanese'. Probably lots of 'i believe's and colons. Also Cassus ending his sentences with katakana, I think? Follow Umineko and put the last world in all caps? But considering his backstory, it sounds more like unusual inflection or a speech impediment. He's got that halting way of speaking.
