Common
Tenora Works
All purpose editor for many files and archives in PSU and the Portable games. While it's focused around PSU, PSP1, PSP2, and PSP2I all have varying degrees of support.
Aqua Model Tool
While primarily for pso2, one way conversion from PSP1, PSP2, and PSP2I's .unj to pso2's aqp and aqn, which can be exported directly to .fbx from the same tool, is supported.