Using main disk partition to upgrade MacOS

Morning all from the UK. I have a 15" MBP Retina Late 2013 running OCLP 2.01 and MacOS Sonoma 14.7. The system runs OK but the fans are basically always on (this is besides the point!). My main disk is a 1TB SSD which has approx 600GB spare. Rather than create a USB installer, I was thinking about partitioning the disk and creating an installer partition that I can select on boot, so the process would be:

1. Create 50GB partition on main disk.
   
2. Use OCLP to download Sequoia, make the 50gb partition bootable and create an installer in that partition.
   
3. Rather than restart, just launch the installer while in MacOS and let it do its thing to upgrade the main boot partition. Then restart into Sequoia and have fun times.

Would this work? Or better to just go the USB stick install route?

Thanks all!