Exascale particle-in-cell (PIC) simulations like Vector Particle-In-Cell (VPIC) face critical parallel input/output (I/O) bottlenecks due to legacy proprietary formats and storage bloat from redundant ghost cells. We present two architectural contributions: a Kokkos-aware staging pipeline that eliminates ghost cell padding – yielding a 67% reduction in grid-based export sizes – and a parallel Hierarchical Data Format 5 (HDF5) backend validated against h5bench in a weak-scaling study up to 896 MPI ranks. Our pipelined architecture achieves file-per-process (FPP) throughput comparable to the legacy binary format, outpacing monolithic bulk-writing benchmarks while isolating collective I/O (CIO) synchronization overheads, establishing a definitive performance baseline for emerging Exascale architectures.