This. You always have the power to change the proposed contract to suit your needs, and let them balk if they don't like it. This assumes it's a contract you can actually edit (whether on the computer or mark up with pen); for non-editable things (e.g. DocuSign contracts), I'm not sure what you'd do if you can't print it out pre-signing.
For the latter, I've sent them a "diff" over email containing the changes I required before signing. They didn't accept any changes to the document itself, but they did let me create a separate document with clarifying language.
