Is it really okay? Wouldn’t that send them mixed signals ?
What signal are you interested in sending at this point? I wouldn’t suggest asking out a woman you have zero interest in. If you truly have never had any interest beyond friendship with any of the female friends you’ve referred to, I’d start looking elsewhere.
People date in order to determine if they might want to get into a relationship with the person. If that is your reason for asking them out, that isn’t a mixed signal, it’s what dating is about. It’s the honest signal.
If you’ve never had any special feelings for any of those female friends, dating them probably isn’t going to cause them to occur. I presume you already know them well.
Are you clear with yourself about what you are seeking? That’s the best way not to send mixed signals is to make sure you know what you are about and then you can communicate that effectively.
If you want to get to know someone but aren’t ready to date them, ask them to participate in group activities or to come to a party with you, something like that that doesn’t come across as a formal date.
If you meet someone who you feel romantically attracted to and want to get to know better then a date makes perfect sense, that is what a date is for. A date is not saying “I want to have a relationship with you” it’s saying “I’m attracted to you and would like to get to know you.”
After dating someone for awhile, that’s when the discussion on exclusivity, expectations etc comes up.