Replacing the I-beam cursor system wide.

[rhubarbpieguy at gmail.com]

Is it possible to replace the I-beam cursor system wide through X?

In explanation, years ago I suggested (to deafening silence), that Open 
Office offer a block/blinking block or underscore/blinking underscore 
cursor.  However, I'd prefer no I-beam cursor in any application 
(browser, spreadsheet, email ... you name it).  If I understand 
correctly, X displays what the application directs.  Would it be 
possible to amend X to display a different cursor anytime it's directed 
by the application to display the I-beam?