I've concluded no, it is not possible and here's why. Sorry if this becomes a long post, but I thought knowing it ahead of time might save others some time and frustration. Final conclusion at the end.
I started off with the BYOD (Bring your own device), put in my IMEI number and it validated fine, says everything's ok. The it tries to tell me that my device has a nanoSIM - it does not. And, it does not give me a chance to select the proper sized SIM even though their DB is messed up. How stupid of programming is this.
I left it there for the moment and came back the next day. Due to the other errors (see below) I had to go through this process a few times. When I came back the next day the website says that my IMEI number was reported as stole and I needed to contact the last carrier to get this cleared up. I thought oh S**t, and this was because I did so many IMEI look ups while trying to get through their buggy web site. Customer service on this new issue was of no help. And since this was a brand new unlocked phone, there was no previous carrier to speak to - OMG. After really fuming about this another day, I thought I'd give it one more try, sure enough at that time, it went through.
However, I still had the orginal problem and call CS once again. When I called customer service about this, they said don't worry I can either go to a store, or complete the order with the wrong SIM size, then call them up after receiving it, and then request a new one of the correct size - they even offered to refund me the second charge of $9.99 - yeah right. Well after playing around with this for much longer that I care to admit, I did find a stupid work around and managed to get it to the point where it did give me three choices and I was able to select the correct choice. Bottom line here, really poor web programming. By the way, I tried this in IE, Firefox and Chrome.
Next after getting through the SIM size issue I then came across the email issue. My email has a "-" in it. The cricket web sight would not accept that as a valid character/email address - WTF. Once again, really poor web programming and same results in either IE, Firefox and Chrome. So I went and created a brand new email without a "-" and everything was fine once again, until...
I entered my CC information , etc and then hit continue. At that point I got a spinning circle that spins forever. After a 45 minute chat with customer service, and listening to them tell me that their website is having problems (no s*** sherlock), they said this could be related. It wasn't, turns out that forever spinning circle was really an error message that IE and FF were unable to display. And only if you did the same thing in Chrome, would you see a specific error pertaining to what you entered. So warning to non-Chrome users, if you see the spinning circle for more than 1 minute, it aint coming back.
At this point I concluded that it was impossible(at least for me) to get BYOD Cricket service through their incredibly buggy website - it's total crap. I then located a kiosk and went there. In 10 minutes, I had new service, without the activation fee (waived because of this saga) and no charge for the correct SIM size. Service wise, I've been pretty pleased. No complaints on that side yet and the transition/registration was simple.