Anything to fight the Gil spammers would be great.
I personally had the following ideas :

1) Only be able to use /tell when using a paid subscription, so unable to spam with trial versions. (this will cost the spammers money each time they loose a spam character)
2) Level restriction before you can even use /tell, maybe one class should be at least level 20 or so (this will take spammers more time before they are able to spam once again after their characters got banned)
3) Word filter option, so that we can add a combination of letters and words to filter out some tells if they reuse the same text with different characters
4) Right click on name and report as Gil spammer, and add an option for controller users as well to make life easier for your customers that actually play the game