I agree with some (but not all) of your post. Upgrading the acid zombie or shocker zombie would make it insanely tough for newbies to start off in the town.
I do however agree that Hulks should be able to bypass (most) blocks. Possibly add an effect that allows the hulk to freely move through (most) destructible terrain with no penalty. (examples: Bushes, Windows, Mutated poppy fields, etc…) Breaking through a wall on the other hand should slow them down. (it’s much sturdier and would actually take a split second to slow them down.) Possibly give the hulk more armor (all that muscle mass.) and maybe a little bit extra health.
Additionally I fully agree with the Boomer giving you a strong scent (until you wash it off somehow.) Possibly make the Boomer exhibit a big Boom when it explodes deafening you as well, and attracting most zombies in a small radius towards you. Being unable to see/hear could be a deadly combination if you do it while surrounded and could lead to more fun.
Maybe some specialized rare zombies that only show up after X amount of days?
Runners: These guys can run up to 60 mph, but attack at normal speed. Incredibly dangerous for drivers who like to run zombies over. These Runner zombies will attack the whole car if it means getting to the juicy victim inside. (Normally show up in small packs but driving away from them may end up with you having a whole squadron of them on your tail.)
Additionally these zombies are actually intelligent and will try to avoid getting run over and will aim for weak points of the car/building you’re in. (These zombies are Uncommon/Rare and can show up almost anywhere, most prominently in the wilderness. Fleeing from them in a city will test your driving skills.) Fleeing on foot is (usually) not an option. (They are not particularly strong)
Buried: (Very Rare) Zombies that have died/are underground. They will pop up one space away from you if you step next to them. Usually these are very rare, but grave-sites seem to have a lot of them.
Brawler Zombie: (Common to Uncommon) These zombies have seem to retained some of there fighting skills. Bites will be replaced with kicks, punches, and even grabs. They have a moderate amount of health and even know how to dodge. If they pin you to the ground they will attempt to spread their infection through biting. (Slightly above average speed, but they shouldn’t be able to run faster than you.)
Martial Master Zombie: (Very Rare to Extremely Rare) If the hulk is pure brute force than the Martial Master Zombie is pure skill. These zombies know an actual martial arts style, and will use these styles with force to bring down their prey. Spending so much time practicing their art there attacks and speed lose no force even after death. In fact they are one of the very few zombies which will not bite. Don’t engage these guys in hand to hand combat unless you know what you’re doing. They have high health (not as high as a Hulk), high dodge skill, and a great attack, with decent speed, and can even swim/climb. (They can’t be outrun in a fair race.)
If you’re extremely unlucky you’ll find a small batch of these guys in a dojo. Normally they are found roaming the city. But every now and then a rare hermit martial master zombie may spring out of the woods. (and if you’re super duper unlucky you’ll fight a zombie who can disarm you.)
(Note: These are also one of the only zombies to have variable melee/unarmed/dodge stats)
Weapon Zombies: Zombies that have learned how to wield weapons. They will swing their weapon around wildly trying to kill you. They don’t really know how to use their weapons though. But if they do hit you can bet it’ll hurt. Additionally they can also block with their weapon. (if it’s possible.)
(Variable weapons from a list are chosen, and yes they can wield guns, but they’ll just swing it around as they don’t know how to fire.)
Master Weapon Zombies: (Extremely rare) Like a mix of the Martial Master Zombie and the hulk. Combining Skill and Power these Zombies know how to use a weapon and use it well. Again you may find a small pack of them in a dojo (or weapon gym/dojo if that ever gets put in.) They start off with a random weapon usable for training/actual fighting.
(Examples: Wooden Sword, Katana, Hatchet, Spear, Nunchaku etc…)
They have variable dodge/melee/weapon skills (medium - high)/unarmed (low to medium at best)
I think this would be some pretty cool zombies. Plus unarmed martial arts battles against zombies would be pretty awesome.