The Agave issue has been brought up before and I tried doing a search to find out about the mineral contents of Agave I found very little else than commercial info and it being described and a sweetener. The maple Syrup is not used for sweetening and it is used mainly because on the high mineral contents. Do you have any information concerning the mineral content of Agave?.
According to Mr. Burroughs the syrup contains a balanced mix of positive and negative sugars that are easily assimilated thus they won't cause the sugar spikes that you mention. Agave is a relatively new product on the market and I would say has little track record regarding it's long time use while the MC has been around more that 50 years and thousands have used it with the syrup with amazing results. There is also the option in the Burroughs book of using sugar cane juice which a recently tried for the first time on the MC and loved it. Anyone living in the US near any large Indian, Caribbean and some Asian Cultures can probably find the fresh squeezed SCJ. The book also mentions the option of Blackstrap Molasses for diabetics but also many MC"ers have found that a table spoon of BSM as a good way to boost energy on low periods on the MC.
A friend that sez he has some very early Burrough books claims that the original MC was with SCJ but only later as it is not easy to find in the US the use of the Maple syrup became standard. I'm just passing on this as hearsay since I have not verified this info personally.
BTW not that it is relevant for the sugar discussion but the best known use of Agave is to make *Tequila*