TG-1: Anyone plan on external add on lenses?

Originally I never actually considered buying the add on lenses for my TG-1. If I want to take serious photos then I'll just take my DSLR.

Then I realized... I always have my Camelbak with me when I go mountain biking.. and many times when I go skiing. (I have a first aid kit, emergency blanket, bonk rations, etc.) So it would be very simple to slip the external lens(es) into that pack.

And since I had originally planned on a new Pentax K-5 with the 18-135mm WR lens this summer I still have about $1200.00 in my camera budget. (Yes... I know the 18-135mm WR lens loses IQ for the sake of the range... But I have a 50mm f1.4, 90mm f2.8 macro, and a 135 f2.8 primes for serious work.)

ANYWAY... So perhaps I might be considering these external TG-1 lenses. Anyone else have any thoughts about them?

SIDE THOUGHT: Might it be possible that the IQ of the stock TG-1 might suffer slightly since it was designed to allow the use of these external lenses? I would not be surprised if the IQ is better with one of these external lenses.

(Perhaps I'll buy one or both of them and do a study to compare the IQ in each case. It would be very interesting to IQ for the same focal length with and without these external lens.)