I spent yesterday trying a couple things to get around needing a keyboard in homebrew to use my installer. I first tried using alternate USBD.IRX and USBKB.IRX files (from games) in uLE to see if this would maybe provide better keyboard compatibility in homebrew (uLE, radshell). Instead this locked up the uLE boot, so I don't think game keyboard drivers are compatible with homebrew.
Radshell 0.8 has some bugs, one of which causes the overwrite question to appear no matter if the file exists or not. After some time I was able to get radshell 0.8 to compile using the latest ps2sdk, and merely commented out the overwrite check. Of course this means that files will be overwritten without question, but for my singular use, this is ok. I contacted radad1 to see if I could release his modified radshell, which should solve your problem and I am waiting for his answer. So hang in there, I might have a way to get the installer working for you in a day or so.
PS2 v9 NTSC, PS2 v12 NTSC, PS2 v15 VESA