R.**Neither a teacher nor a native speaker.**
If you use be, you will need to use depending
Its replacement would be depending on how you use it.
This is a substandard sentence.
Its replacement would be what depending on how you use it?
The following is possible:
"Its replacement would be bigger/different/stronger, depending on how you use it."
The rest of your post is good, and contains better alternatives.
P.S: I believe it's "If I said.... would", not "If I would say... would" - but maybe I'm wrong...
You're right. We don't say, "If I would say..."