Yeah they don't need to be build defining like the +% OP were, but if I had to come up with something nice but not mandatory quickly I'd say:
% damage (say 5% steps) piloted ship for Combat; (the least universally useful, to go with the least universally useful tree)
% damage reduction (5% steps? 3,3% steps?) for fleet - since that's something that every leadership user, fleet and self-piloted carrier, can use for Leadership
% fuel use and/or % sensor range (3,3% for max of 10%) for Technology (because everyone likes cheaper travel and more sensors)
% reduced CR recovery cost (3,3 or 5?) for Industry (because cheaper CR recovery is kind of the missing ingredient for a pure Industry playstyle and every playstyle will appreciate it)