I have had the pleasure of working with Leó on the Lubuntu project for several years now. He was a Lubuntu Member until recently, inherently granting him Ubuntu Membership. In my own capacity, I would suggest to the Ubuntu Membership board that this is simply a reinstatement of existing privileges, and perhaps a full process may not be necessary (especially given the recent docket of applicants).
Leó is a kind-hearted, rational, and skilled contributor who has contributed countless hours to ensuring Lubuntu stays (relatively) bug-free. I can not count the amount of times he has helped during release week to get the ISOs tested, brought something to the attention of myself and other Lubuntu Developers to move the needle forward, and tested items not even on our list. This (often times thankless) work is critical to a strong Ubuntu, and I cannot even begin to express my gratefulness for his significant and sustained contributions.
To my understanding, Leó and @guiverc are key architects in Lubuntu’s extended testing checklist (conveniently, our Phabricator instance is down for maintenance so I can’t link it). Let me assure you, this checklist is extensive, covering no-network installs, EFI vs BIOS installs, different filesystems, etc. I am deeply impressed every single release when they complete this extensive, 20 or 30 item checklist. Leó is instrumental in the creation and maintenance of that document.
I wholeheartedly support Leó’s transition in interest, and as I told him privately, he can always call himself a Lubuntu Member Emeritus. I really look forward to working with him in the wider community, and I am incredibly thankful that he chose Lubuntu as his entry point. My personal hope is that he does not forget his roots. 
I absolutely and wholeheartedly advocate Leó for Ubuntu Membership, immediately. We would be incredibly fortunate to have such a dedicated contributor join the roster of Ubuntu Members. If anyone deserves it, Leó does.