hello Eamon,
I can make some of my Efforts on it to just check out that it can be implemented or not on a custom form! But Not Guaranteed Because The Development Team is very busy with wplms 4.0. we are transforming our theme to REACT. this will become the super fast theme. once we release this, we will work on the other feature requests.
we have many customization requests so i hope you understand.
i have just searched for your requirement and found something that can fulfill your requirement.
please have a look:
https://wordpress.org/plugins/advanced-xprofile-fields-for-buddypress/
you can make use of this plugin this will help.
now you have the option to set validations for all fields: http://prntscr.com/qiussy