I don't know you you want this so hard but nothing is easier than this.
Go to the FMCB-Configurator than "Configure E1 launch keys..." and configure the "AUTO" entry to the path to your ELF-file. Save the config to your MC or mass (if you use usb device for booting things).
PS2 SCPH-70004 V12 PAL + HDCOMBO + 160 GB Samsung HDD + OPL 0.9.1
PS2 SCPH-70004a V13 PAL Satin Silver
2 x Official Sony 8mb card +FMCB 1.8c + uLE 4.42b
Datel Max Memory 32mb card +FMCB 1.8b + uLE 4.42
Memor32 + Memento FW 1.2e