Lexos will use buddy system algorithm for page allocator. I am still learning buddy allocator, since, I don't find much free time nowadays. Flaws in memory management algorithms will make an operating system weaker. So, I am taking much time to learn and design buddy allocator in my OS.
Lexos will have VMM on top of PMM. PMM (Physical Memory Manager) will service the applications and kernel by providing and freeing page frames on demand. The allocated pages will be mapped into virtual address by VMM (Virtual Memory Mapper).
Edit: As for the time being, I have planned to use stack based approach to manage physical page frames. Later, I would use buddy allocator. Though, I am thinking of using a modified version of stack-based approach, which would have individual stack that holds free pages in the order of 2^n.