Well, Bruce Willis is the only constant through all of the Die Hard movies so, yeah, I'll go with his ideas and recommendations on the character and franchise over anything else. Though for a touch of humor, see Kevin Smith's experience working with Bruce Willis on the set of "Live Free or Die Hard" (where Smith has a small role as a hacker friend of Justin Long's they seek out to help them.)
Relevant portion begins at about 8:00 and continues through the next portion of the uploaded video. (Back story to the segment: Evening With Kevin Smith 1 ended up being a successful "demo video" for Smith as he came across as very genuine in it, as a result he got a lot of audition offers, one being for Die Hard (4.) Before the audition he "re-wrote" the sides to a dialogue he was more comfortable speaking and offered those as his audition. He didn't feel the audition went well but eventually was given the part as Warlock presumably as "payment" for the re-writes he offered which the Director decided to use (but ultimately was discarded in favor of something else as revealed in the story of the video.) It's really an interesting look at what it was like for Kevin to work with Bruce Willis in Die Hard and in a future edition of "Evening With..." Smith recounts his experience in working with Willis on "Cop Out."