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Be careful with DHW set that high, caution guests, especially small children, elderly adults, to the hot water being "hot" It only takes a few seconds to get a burn at 135°

Most single handle tub shower faucets have a temperature function now a days.

Piping looks fine for maximum input from boiler to tank.

From what you're saying, when the aquastat calls for heat, it sends 24 volts to the Honeywell zone valve to open. Once open, the end switch on the Honeywell zone valve closes and turns on the boiler. And there's no priority. If you have plenty of hot water during the heating season, maybe you don't need a priority control scheme.

Hi, My approach isn't brand dependent. I'd make sure heater I got had a full, non pro-rated warranty, and hopefully good support where you are. I'd get only a six year warranty. I'd make sure the tank I got was able to accept a second, full length magnesium anode rod, and make sure the rod it comes with is magnesium, or is changed out to one. I'm not a fan of having aluminum in tap water. Beyond setting up the tank, I'd make sure the tank lived at water pressures in the 40 to 60 psi range without any big fluctuations. Finally, I'd make sure it got clean air for combustion. These days, replacing a tank can run thousands of dollars, which is why I try to keep older tanks that are in good shape, going. 😊

Yours, Larry

You might be interested in "Thermal Purge". The L8148A is an analogue control. there is no "Brain" or "Logic" in that control to "Decide" to leave the burner off. It is as efficient at what it does with the limitations of analogue technology.

Energy Kinetics is a company that understands your idea of "Wasted Energy" as you stated in your original post. They have built into the electronics of the control that replaces the Aquastat Relay, a logic that actually shuts off the oil burner (or Gas burner) early and keeps the zone valve open (in your case) or zone circulator pumping to "Purge" the boiler of that 160° heat into the last zone that calls for heat. That way the boiler won't be left at 180° or 160° at the end of the previous cycle to slowly cool off my letting all the heat from the boiler exit up the chimney. The hot boiler water will be circulated into the water heater or space heat zone for a predetermined amount of time calculated by the control's onboard software. This is only one of the ways that System 2000 and other EK boilers reduce operating cost compared to the boiler brand that you have.

All that said, there is a way to build a holding circuit to purge the left over heat in your Weil McLain into the system, but it can get tricky when you have zones. Some others with single zone systems have had some success with lowering their fuel consumption as much as 5 to 7% using DIY thermal purge. @jesmed1 is one that comes to mind in this post

BW seems to hold up the best.