Hi there! I too shoot a lot of IR and use RT exclusively for raw conversion and pre-processing my photos (all my photos on Flickr have been shot with IR-converted cameras, and converted with RT: Marcos Capelini (infrared) | Flickr). The 5000 limit for the tint slider has been a problem for me as well. I’ve been able to trick RT into getting almost neutral WB for IR by using DCP profiles like Gabor did, but the result is not always perfect, due to reasons already explained above. Unfortunately, the camconst.json workaround is not feasible for me, because it would affect “normal” (visible light) photos I took with the same cameras before they were converted to IR. For those who have no experience with IR photography: a neutral WB is very important to obtaining good results with the “false colour” technique, even more so than it is for monochrome IR photography.
RT is great for IR, and the channel mixer allows me to do the blue-red channel swap that is usually necessary for colour IR. I have a number of RT presets that I use for B&W and colour IR, and they would work even better if I were able to neutralise the remaining colour cast at the WB stage. I vote for extending the limit of the tint slider, if that brings no problems.