My answer is to apply monetary economics. I shall assume that technological or bio-technological solutions to increase the ability of the planet to dispose of significantly more waste heat than it does today are not feasible or desirable.
Secondly, with all that MF power, lets get people making use of it to develop a spacefaring civilisation!
So my recommendation to the commission is roughly as follows:
1. The (world) government shall establish a currency for which one unit can be redeemed against the rights to operate a MF that produces one unit of waste heat. This is similar to todays money which is redeemable against future consumption - now we explicitly tie money to entropy production. This currency replaces the current fiat system. Money based on energy usage has been quite widely discussed in the context of peak oil. This situation is essentially the same.
2. The quantity of currency is fixed according to the capacity of the earth to dispose safely of the waste heat, so its different to todays money in which the economy is not energy constrained is is more constrained by supply and demand of finished goods.
3. The government mandates that FI with their fantasticly secure technology that cannot be reverse engineered add a 'waste meter' to each MF that is loaded with the credits/money and will refuse to produce power when the credits run out.
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These constraints do not apply for MFs used off-world, and this stimulates movement of power hungry manufacturing processes, and in time, residential establishments to move off world. Asteroids and comets are fetched to power the off world MFs. Since the off-world economy is not energy constrained, it uses its own forms of private currency similar to modern bank created money/credit. These currencies float against the terrestrial currency.
5. Because the rights to production of waste heat on earth cannot increase, those trying to save money in terrestrial heat-currency may be subject to a negative interest rate or inflation in the terrestrial currency if he actual quantity of waste heat that can be safely disposed of by the planet declines due to government decree. When the global heat production limit is increased the terrestrial currency appreciates versus the off world ones, and vice versa when the terrestrial limit decreases.
6. The 10% remaining on earth must spend their terrestrial currency on power production to maintain their standard of living, but also on importing finished goods from off world manufacturies (the data centres may also be off world). The off-worlders selling goods to earth get in return terrestrial currency that they can only redeem by either coming to earth an living for a while (many off world workers probably don't live off world all the time), and by importing stuff which cannot easily be manufactured in space - mainly stuff like quality food and drink, works of art, things like that. Ultimately to work, there has to be an equilibrium in which neither the off world nor terrestrial economies run a persistent trade surplus. 130