Superceding Return to Change Form 1040 Filing Status from MFS to MFJ?

I'm contemplating trying to do a superceding return in the wake of the student loan forgiveness announcement.  But I'm concerned that it may not work?  In my situation, spouse and I file separate timely 6-month automatic extension for the 2021 return, so the original due date for us is October 15, 2022, which hasn't come yet and e-filing is still open.   Spouse, however, already filed a married filing separately return and got a refund, while I haven't filed anything yet.  The superceding return intended here is to change this to a marriage filing jointly return, and there will be an additional refund due in addition to student loan forgiveness eligibility.  Will e-filing a MFJ even work in this situation, or does it have to be a mailed paper return at this point?  Will they just figure out to reduce the requested refund by the amount they already paid, or (if mailing) should I include correspondence to explain what we're doing?   I don't want this processed as a 1040X amended return (albeit one filed before the extension due date) because that is usually handled by IRS as a request for an account adjustment, not as a return filing, and it will leave me on record with no return filed.  And I don't think the student loan forgiveness program is going to be smart enough to consider eligibility based on amended returns, which can be filed up to 3 years after the due date...   Comments?