I believe it would be safer to wrap that in a function:
as.character.quosure <- function(x, ...) rlang::quot_text(x)
Reason is that your construct would capture the rlang::quo_text function at time of installation and places that in the installed package. The consequence of that is that any update to the rlang package won't be reflected in yours. You would still have the old version of rlang::quo_text in the installed package. Hence the version of rlang::quo_text would be dependent upon when the user installed the package. That's why it's better to wrap it in a function. That way you point to whatever version of rlang is installed at the moment you use the function, as opposed to the moment you install the function.
This is similar what you would do when you add a new S3 generic and copy the old one into a fun.default method. For reference: your construct was once suggested in the R extensions manual, but that has since been updated:
https://cran.r-project.org/doc/manuals/R-exts.html#Adding-new-generics