there is some logic and also some truth about your proposal, but may i tell you, with all due respect, this is "old school". some 30 years ago, when the first mechanical stringing machines found their way into romania and topspin started to be the "rule" as shown by greats as borg and vilas, my coach and stringer used to string the small sized wooden sticks quite stiff (good for topspin indeed), that is as high as 30kg in the mains and 28 kg in the crosses (yes, borg was playing like that! - with natty gut nevertheless), and the outer two mains he used to string about 2kg less and the upper and lower 3 crosses also about 2kg less than the rest of the strings.
this gave a little bit more power but kept the control and the spin of the rather stiff stringbed, as you can imagine - small headsizes and quite dense patterns.
today i do still string the same, with a little bit less difference, but due to the increased stiffness of the strings i have gone down to 22kg (100sq.in headsize) with the poly mains, the outer 2 mains being strung at 21kg, and the crosses are strung at 21kg with a multi, the lower 3 crosses and the upper 6 crosses i do string 1kg lower.
i do string the upper 6 crosses lower (something i heard that davydenko is also doing) because i tend to regulalry hit the upper third of the stringbed and therefore need some more softness up there, trying to extend the sweetspot upwards.
even if the numbers are quite low in regard to your suggested 70lbs (around 33kg i guess), i still get good spin on the ball. personally, i'm too old to string that high, i would have difficulty hitting a "heavy ball", i'd most probably just produce spinning sitters, and my son is just 12, so high tensions are not advisable. if you have the power yourself and you can keep it coming or going for three sets, i do agree that you get a lot of spin from a stiffer stringbed, but even pros don't go as high as 70lbs, so probably the "truth" is more close to the 60s range.