If you're really married like you claimed, and still not divorced, you do know what's the benefits of marriage?
If my crush wants to stay as FWB, so be it. If she wants to start living together and be an unregistered de-facto (if she can secure her own PR) then so be it. But I'm happier if she says yes and we get married.
Only small minds would tell a single person to stay single and not have a family of his own. Many old people have given me better advice on getting married and settling down after my divorce - if there's something about her that's worth remembering (her beauty, sex-appeal, kindness) then it is worth putting a ring on her even when later on she starts wrinkling and getting grumpier due to menopause. The older and wiser you get, the more you're able to withstand her drama. That's just life as it is.
As for divorcing my ex, I have to justify it as someone who I just can't build a lasting memory of - she's not a looker, has no sex appeal, unkind and basically rude. At least if I marry my crush I can tell people 30 years later that she was the kindest, sexiest and prettiest girl that I'm lucky to marry her.