If its only the login page and you can't accept the course / category theme functionality, i.e. the front page will still be Moove, then no, can't be done unless you port the Moove login code / CSS to the other themes. This is not a trivial thing to do for an experienced programmer and would be an even longer task if you now ask 'could you list the steps I need to take'.
Themes
Common Login page for all themes
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