What I believe Richard is saying is that he enjoys being a designer and has no desire to move into management. I see no problem with this, and I fully expect that most anyone else who shares this point of view and is happy to continue in the same role throughout their career, is also willing to accept the fact that they are never going to recieve the same salary as executive management.
There is no rule or law that states that everyone who enters a company must continue to be promoted ad infinitum. Far too often, in fact, I have seen great designers and engineers promoted into management roles that they didn't really want simply because they were the most senior person available within the company. Whenever this has happened it has been the department that lost the engineer or designer that has suffered, because they are rarely replaced and if they are then at very least the replacement will take a few months to get up to speed. Also, from my observations, really good engineers &/or designers in this situation often don't make good managers because they are usually wishing they were actually back doing the work rather than talking about it.
As for actual interview questions though, just think about the things that are genuinely important to you as an employer. e.g. If you want to know how well they know the software, then ask them some technical questions about the software, or ask them which version/s of the software they've worked with. (If the most recent they've used is R14 then you know you'll have some training ahead of you.) Ask if they've just used ACAD 'out-of-the-box' or if they're used to it being customised heavily to suit their job. (Both have their advantages - someone used to using it OOTB will be more productive more quickly, whereas someone who can customise it may bring some very useful skills inbto your office. If they're used to it being customised though, be sure to ask if they did the customising or if they had someone at their last office who did all of the customising for them.)
Regarding the more personal questions about interests, hobbies, etc. - unless you are genuinely interested such things, or are actually concerned with how they might fit in with other staff in your office, then don't bother asking. In reality, it's little to no business of yours as an employer what your employees get up to on their own time, provided it's not an activity that may damage the reputation of your business. Of course if your office is one where many of the staff spend time together socially, then this may make the questions more appropriate. e.g. if the interviewee responds with "I'm into motorbike riding and stamp collecting." then you may (if you know your staff well) be able to say "Ah, a few of us have bikes, we try to get out for a ride together every month or two." No need for any more than that, but it will serve to set the interviewee at ease a little.
I guess mainly just keep in mind that the aim of an interview is to gauge suitability for the role from both a technical and social standpoint. If a person is technically very proficient, but also very arrogant then I'm not likely to hire them as I find such arrogance abhorrent - there would soon be a major clash between me and them so for me it would be best to avoid the situation in the first instance.
Also remember that the purpose of an interview is not to see how uncomfortable you can make the interviewee. I've seen people not turn up even when they got a second interview, because the first time around they felt the interviewer was so intimidating or condescending that they couldn't imagine themselves working in that environment.
Anyway, I hope that ramble helps somewhat.