I am going to preface this statement with the fact that I have nearly 1000 hours of dual instruction given, the last flight school I worked for/through was 61 and 141, and I have had a few students that got there licenses in 6-8 weeks.  One student was instrument rated in about 3 months time (all, part 61), so it is possible if you are dedicated and disciplined.

Hopefully I can give some helpful advice on both of your questions.  As far as doing the accelerated flight training with your 'normal' CFI, it should not be a problem.  First and foremost, however, you should ask the instructor a few basic questions that will help you make a decision.  One, how many students has he trained and passed; what is his pass rate first time around.  Next, is he willing to tie up his schedule with you that much.  More than likely yes, but if he already has 5-6 students, he may not be able to (instructors, as well as most other professional pilots, are limited in FLYING only 8 hours in a 24 hour period).  Usually, not a problem, but there are a few times you must cut a flight short due to heavy flying loads.  I am glad that you like/get along with the CFI, but try to remember, it should be more of a business relationship; money for services rendered.  Do not get me wrong, I still speak with and go out with several of my former students (football games, drinks, etc) even after I moved 200 miles away, but while instructing, it was all business.

Now then to dive into your next question about purchasing an aircraft.  Again, ask your instructor some questions.  The planes you are inquiring about are great GA aircraft, but the insurance company (which REALLY dictate what we fly) will require you to get at least 25 if not more dual instruction in with your limited time/experience.  Question one in this regards should be the instructors own complex time and high performance time.  Complex is generally not a problem, it is the high performance that a lot of new instructors have a problem with.  Another is time in type (PA32, PA32R, C182, C206, etc) that again, the insurance company WILL require for the person you get your required dual instruction from.

Now then suggestions on planes.  You have practically 0 time, so you are not biased towards any particular model.  I do not know your finances, but if your idea is to get time in a plane and fly you and your family/business partners in, I would suggest a fixed gear aircraft for now.  In this range you have several to choose from.  The four seat variants will be more easily insured by you (not to mention cheaper).  TRUE four seaters (four adults and decent range of fuel) would be C182 or Cherokee 180 or Dakota or Cirrus and Lancairs.  There are others, but I do not have 1st hand knowledge of loads, but I would think that the Grumman Tiger would fit the bill.

If you do decide that your mission, 80% of the time, you need 5-6 seats, you have fewer  fixed gear options.  C206 and Cherokee 6. 

I would suggest if you decide on a four seater, to go for the C182.  This plane has been known for decades as the best all around GA aircraft out there.  It is easy to fly, especially if you are used to flying C172's.  And if this or another four seater is your choice, I would seriously consider purchasing the plane and do all of your training in it.  Now, buying a plane is not like buying a car, it is more like buying a house.  I say this because, airplanes are more of an investment.  If one is not maintained well by the previous owner, you will have VERY high MX costs.  So, I strongly suggest a prebuy inspection and although maybe more expensive in the short run, an aircraft broker/dealer to assist in your search.

My two cents.  I hope this helps and that I have not confused you.

Brian