Ok, here's a slightly more fancy graphical field editor. It still modifies the game in memory, but it's dead easy to use. You'll probably need the .NET framework to run this one. I'll do one that permanently modifies it later (it's not hard, just fiddly).
Some quick instructions: Load BLIC and start up any match. Then start the fieldeditor and click on 'Extract from Game'. You should see something like the first picture. Change the field to your desired one by clicking on a fielder, and clicking elsewhere to move him. Eventually you'll get a nice choice (second picture), so hit 'Copy back to Game'. Then, move back into BLIC. After you've bowled the ball or reverted the field positions, the change will take effect (as in the final exciting picture).
Let me know if it works. It's still a bit rough, but I wanted to get it out while I could. Oh yeah - it only edits custom field 1 for now. The same theory works for any other field too, so it's just a matter of adding the option.
And here's the download: