Re: BuddyPress can’t see bp-themes
Well, yes, that’s the best way for the majority of BuddyPress users, I suspect.
However, you can work around by duplicating the BP Member Theme folder (/bptheme) into /wpcontent/themes. You don’t need to do anything else, but this should populate the list for you allowing you to save the member theme.
Or, if you know what you’re doing, apply the patch to fix this problem to your current release manually – https://trac.buddypress.org/changeset/1601/. If you do not understand PHP I would not recommend you do this, just in case you accidently introduce any errors.