I wouldn't be surprised if quarks and leptons (electrons) contained the same base element. If, at the beginning of our universe, a soup of base elements separated from their stabilising energy charge tried to return to their original 'perfect' state, it would make sense that these elements would 'bind' according to their energy level. Already-charged (positive) elements would bind with lesser-charged (negative) others, creating hadrons, and these in turn would group according to their own respective 'polarisation' (charge). Already stable hadrons would reject any further binding (each contain three quarks, two 'up' and one 'down', or vice versa) - I wouldn't at all be surprised that electrons (leptons) were unbound but charged quarks ('base elements') 'left over' from the initial 'soup construction' stage, once it was completed. Electrons still attempt to bind with an atom's nucleus (and its protons and neutrons), but the 'rejecting force' ('binding energy') of an atom's nucleus (and its individual hadrons) and its opposing charge, prevent them from doing so.
This fits in with the thought that gravity is the 'base element' minus its initial energy, or the effect caused by the 'base element' trying to capture energy enough to return to its initial 'perfect' state. A base element trying to recuperate its initial energy either succeeds or fails depending on its energy level in relation with its neighbours - once no further hadron binding was possible, everything else that followed (atom construction) was but consequential.
Addendum: I can't help but observe that the 'binding force' between stable elements decreases as we advance further along the atomic construction scale. Binding between quarks (creating hadrons) seems to be the strongest, but it is lower between charged hadrons (neutrons and protons).
I also can't help but notice that protons (containing two charged, or 'up' quarks) alone, unbound, are the only element that can retain stability; neutrons are overcome, or are 'evaporated', by their own forces. Does this mean that a stabilised hadron has to 'feed on' (or be 'fed upon') by its neighbour in order to maintain stability? Neutrons contain one 'charged' quark (or 'up' quark) and two 'down' quarks; although a neutron has greater mass (?), the single 'up' quark (that seems to be the instigator of the binding energy) alone doesn't seem to contain energy enough to keep the quark formation together. It would seem logical that a neutron needs to 'feed' on a proton's two 'up' quarks; together, a proton and a neutron together contain three 'up' quarks and three 'down', thus balance each other perfectly. Furthermore, consider that when a 'negatively charged' electron, when introduced into a proton, creates a neutron: it would seem that a 'negative' (no energy?) electron 'saps' a proton's positive energy (transforming one of its quarks into a higher mass 'down' quark. This seems to fit into the theory that even a quark has a 'stable state' of its own: either it is a 'base energy' (gravitational force) containing no 'electrical' charge, or it is an (equal?) balance of base energy and charged energy. 'Base energy' seems to be the most stable of the two, if a hadron's charged energy is released with the introduction of additional uncharged 'base energy'. This is all beginning to make sense.