Don't touch that nib!!!

You can in fact get line variation. All that you need is a bit of time on the learning curve.
The fact is that the Sailor is a very wet writer. To get the line variation, think writing with not really touching the paper.
My "conversation" with myhand goes like this as I do a bit of warm up before writing music with the music nib.
Get a lighter touch. 
write music symbols and words for a few lines...
No, still lighter touch...

write more lines...
LIGHTER TOUCH YOU FOOL. YOU CAN STILL FEEL THE PAPER TOUCHING THE NIB!!!


write a few more lines...
FINALLY, YOU'VE GOT IT!!!

The music nib takes the lightest touch of any pen I've used. I am BTW, using it to write music. This means, I am writing "open body" notes: whole notes, half notes and lots of markings. I have way too many whole notes for my personal playing taste, but this is a beginner's book project.
So, before you do the irreversible, give the nib a chance. Perhaps you can find a drier writing ink for your pen. Sailor ink flows a bit less than Pelikan Brilliant Black in my pen. I have another Sailor where the opposite is true, so that is not a statement of how the pen functions.
I'm happy with the flow of the Pelikan Brilliant black because I'm writing in a very dry environment on paper that seems to require more ink to have the writing stable on the page. It is the worst batch of manuscript/ledger paper I've ever owned. All that the ink choice means for me is that I'm not able to recommend a good choice for you.
And, before you use it on a "real", (i.e., non-practice type of writing) non-music project, you might just need a bit of learning. I found after practicing every day for two weeks, I got the muscle memory down pat, and learned the right feeling in my hand. It is now there on a pretty ready basis, even if I don't use the Sailor Music Nib for a week at a time.
Good luck and let us know what you decide to do.