Indirect fire weapons, please! Something that could launch the pipe bombs or more effective explosives would be fun. Different warheads like shrapnel, high explosive, napalm, etc. Mortar tubes aren't super high tech (aiming systems are another story) but crude tubes are pretty reasonable in the zompocalypse.
I've also wanted static emplacements for the longest time too. To whet my appetite, I sometimes manually use the turrets in-game but it's not as fun nor gratifying as a SMG-based light machinegun or AK-based medium machinegun fed by a belt. That would be cool and realistic for people who prefer setting up a permanent, defensible base.