I think you’re a teensy bit overcautious there! ^^; But, you can make it to level 60 with no scripts. People have done the journey before. But, personally, I’d rather not. >_> It’s just very useful and helpful throughout, both during lessons, reviews and inbetween.
Now I don’t know how I could do my lessons without the Keisei-phonetics script! (only got it around level 25+). Even if you don’t use anything else, this script really helps you understand the on’yomi reading relations between kanji. So, this is something you don’t wanna be without, imo. Suddenly, the on’yomi makes sense!
Then, of course, there is the Item Inspector that I’m reliant on for getting at those leeches. I wouldn’t have managed to address them without it. ^^ (I’ve gone from 170-ish leeches to 98 leeches thanks to this! 
)