Paul Hettinger, DMD (retired)

Implant.  While what you propose about moving 17+18 forward has some logical appeal, I have never seen it done successfully in 30 years of practice.  Implant.

ALL restorative dentistry is elective.  You can survive without any teeth at all.  I never tell any patient that they "have to" do anything.  Hey...it's your money, your mouth and you are the one who has to live with the decision.  That said, please note that when you lose one tooth, you lose the chewing power of two teeth.  The missing tooth's antagonist (chewing partner) cannot function against nothing.  Do teeth super erupt in the absence of an antagonist?  Yes, nearly always.  Mainstream dental opinion is going to be that you are better off replacing missing teeth.  I agree.  How you do that (and if you are going to do that) should be your decision.  Be sure you get all the facts before you decide what makes sense for you.

Define "best".  There are a lot of factors to sorted out according to YOUR priorities:  cost, esthetics, invasiveness, treatment time, number of visits...etc.  I always advise my patients to fix their biological teeth until they can no longer be fixed. (It's never too late to "pull" it.)
I have done hundreds of cast posts and crowns and never regretted it.  The most important opinion when choosing between feasible treatment modalities is YOUR opinion.
'Hope that helps.

This question cannot be answered definitively in the abstract.  Your case will be unique and not optimally answered by folks like me, on line.  If esthetics (and not finances) are the real issue, here is the question to ask a dentist whom you are considering:  In the method you are suggesting, how much assurance can you give me that the gums between the teeth  (embrasures...little triangles) will continue to look good?  Are you prepared to do connective tissue grafting if indicated for optimal esthetics?  Parenthetically, it is easy to make beautiful teeth on either bridges or implants.  The challenge is making the residual gums and the apparent emergence of the prosthetic crowns from the gums look natural.  Look in the mirror and imagine yourself with and without those little triangles.  Ask about emergence profile and creation or maintenance of embrasures.  Then compare the fees to the anticipated results and estimated longevity.  'Hope this helps!

I have never seen a repair of this kind last long term.  Be sure be ask the dentist how long he/she will stand behind the repair.  In the original construction, porcelain is fused onto the prosthesis at ~1700 degrees.  That sort of process cannot be done in the mouth, and anything short of that I personally have found to be quite temporary.