you can make a picture to be the carrier name.
like this on my status bar
where it has my name where the carrier should be, that's just a png image file. you can make a png with the colored carrier name and the half maple leaf. to do that, just use a photo editing program like photoshop or gimp, make it like 55x20 w/ transparent background. add the text and the image and save it as the default_CARRIER_"your carrier".png and FSO_CARRIER_"your carrier".png. then move them to /System/Library/Carrier Bundles/"your carrier"/ on your phone.
not sure on the keyboard thing
and yes, you can change the text on the unlock slider, i just don't know how to.