If your workers are independent contractors, you may be deluding yourself if you believe that you're in a "serious relationship" with them. If they find a client that pays them more, they'd be stupid not to dump you. You can't demand that they work exclusively for you, work extra or unpaid hours to meet your deadlines, etc. (If you could do that, they'd probably meet the legal definition of "employee".) Offering someone like this equity seems like a strange thing to do. When equity is offered to employees, there's usually a vesting period to give valuable employees an incentive to stick around. Contractors, on the other hand, tend to be short-term.
Also, statistically speaking, equity in most startups is worthless, since most startups will eventually fail. The chances of your company becoming the next Facebook and making its shareholders rich are tiny. So your contractors would not be smart to accept any less payment, no matter how much equity you offer them.
Finally, there's all sorts of tax law that grants favorable treatment to "employee stock option plans" that probably wouldn't apply if giving equity to non-employees. You'd really need to figure it out with a lawyer and/or a CPA.