So usually the logic is that if a higher spec car already has cruise control it is very simple for people to just add the controls for cruise control and it works (in most cases). If however there is no support from other models it is not recommended. It certainly is possible, but often the alterations and scope of work is not worth it.
Im hoping others chime in for advise, I'm not too well versed in it and was looking into adding cruise control in my Altis 1.6 until I've seen that they could not even do it in the special edition with the auto gearbox and was only added in the CVT one (if I remember correctly).