Well the question is... how?As i said above i tend to believe that if Constantine Doukas had succeeded in his coup then we might have seen a restructure or the Thematic system in order to modernise it and cover its weaknesses...
The strength of the themes as I understand it is they provided a reasonably effective military force (won as much as it lost) on the spot to confront enemy invasions. This would possibly weaken the enemy but more importantly it would slow them down so that the real army could arrive from Constantinople and fight them before they ravaged half the empire. So defensive.
Assuming that they're still at the height of their medieval power, you are going to think offensively. The basic dynamics are pretty obvious. I have no idea how accurate wiki's Byzantine economy article is, but it throws around a lot of numbers and has a few major sources (Treadgold for instance) and online papers.
You want an army that is probably going to be campaigning a lot. Professionals. But also one that won't revolt if the other guys offer more money. At the same time you want to establish some internal defenses and you always have that two-front problem.
Politically you don't want the aristocracy growing in power enough to muck things up. But you also don't want to bring all power to the peasants because then your farms stay small and you can't take advantage of economies of scale for agriculture. You also want to increase your population if possible, having the aristocracy kick out the peasants who flood the cities is one option. It's an interesting problem. I can think of creative ways around it (and indeed, have written them into my own TL in Spain) but not that are feasible at this time for the emperors in Constantinople.