Dead and Back features only five stats - Aim, Strength, Quick Tech and Wits, and each is rated from one to five in turn. However, this has the unintended drawback of making characters all too similar, and limiting the types of creatures that can be modeled. Thus it may be necessary to change some of the numbers, and possibly even add more attributes.
While I rather like the system as it is now, I see three main strikes against it. Characters show very similar abilities by the numbers, despite
Dead and Back began with a simple combat system and was originally going to be a more action and adventure sort of game. The idea of zombies being the preferred target then morphed it into the darker form it is now, with the deadening and lucidity traits added for that effect. This is also when I codified the idea of a minimum number of traits to define a character. As PC could be replaced in five minuets rather than an hour, the game could allow for fairly high body counts amongst players.
A notable feature in all my games is that I try to avoid "dump stats" and and overpowered attributes. In D&B this is managed by having all the vital statistics preform useful functions, and most are averaged together to produce the derived abilities like "up-rise" and "animus."
Aim was a central component of how the new combat system worked. To offset its great importance, and thus discourage simply maxing it out, this does not feed into the derived attributes.
Dog sized aliens we not originally part of the setting, nor in particular wildlife. My first idea was more of a steampunk zerust, with reanimated corpses fulfilling the role we see industrial in today. However there is apparently a deadworld for the game All Flesh Must Be Eaten with this idea ("Frankenstein 1935" from the Worlds of the Dead source book), and the game "Unhallowed Metropolis" goes this route as well. Hence I changed to my other idea, a more futuristic world with zombies.
The German Sheppard sized "Planetary Citizens" don't fit so well on a "One Child /Three Average adult /Five-Olympic" scale. Nor does this really work for other non-human threats like feral dogs or resurgent large predators.
While the averaged abilities do limit min-maxing, it presents an opposing problem instead. Strengths and weaknesses are a bit too even, and on paper characters look very similar. A highly technical character may be able to carry more stuff than a strong one.
The original intent of that, by the way, was its more a matter of efficient using your carrying capacity - and a smarter person keeps things more aces-able or optimizes what they need. However, its all interpreted as kilograms of weight to keep things simple - encumbrance is often one of the first rules overlooked in most games anyway.
Only one aim attribute means one character is as good with knives as they are with guns. Furthermore, a scrawny and slow character who shifted points from quick and strength to boost aim is still a master martial-artist.
The seemingly simplest concept would be to make the statistics rated from one to seven, with an average of four. This would allow one to be a subhuman/child level for animals, and a seven for things only a bit stronger than humans. (Though some other modification would be necessary for even greater strength.)
The possibility of having a much higher aim stat may mean that a new limit must be placed upon it. One option would be to make the attributes bought from a pool, rather than shifting around a pre-set number. Another is to make two Aim stats - one for close combat, and one for handling ranged weapons. This second option would also allow for more combat specialization without using up valuable skill or Special Ability slots.
A more radical concept would be to remake resolution along the lines of the combat system. That is you compare the attribute ranking to the difficulty, which in turn determines the type of dice you roll in the pool. However, while this would streamline the game to one core mechanic, it would mean re-evaluating the methods behind everything else in the game, which for the time being seems to be an unnecessary amount of work.
Perhaps the original range can be retained, but new dice substituted as the scales change. Sub-human attributes could be based on rolling a 4 on a d4 (25%) which is a slight step down from 5-6 of a d6 (about 33%) or some range of numbers on a d8 (6-8: 37.5%, 7/8 = 25% etc.) The reverse can also be done for larger creatures, say on a d8 five to seven is one success, and an eight two.
A variation on the above - make d8s the default dice for most rolls.
Some more focus on personal details, and a battery of personality test style questions may help as well. It won't change numbers, but it will make manners more distinct. Specialized or personalized equipment of some type may also help make characters unique - and give the GM some control via the distribution of parts.