Missing external pump and expansion tank

Hi all,

Purchased a new build duplex a few years back that has a radiant heating system and a high efficiency boiler. The duplex is 3 stories (basement, main floor, top floor) and has 4 heating zones (basement, main, and two on the top floor). Past couple years have had some annoyances with hot water where the water would turn cold (when washing dishes for example) and would take some time to turn hot again. On rare occasions (couple times a year), this would result in an error code on the boiler which required a restart. Had the home builder out for these issues who made some adjustments to the system, but otherwise said everything checked out.

More recently, had a problem with the basement heating not coming on. Had a HVAC technician come out and they had to replace a valve that was not opening. This resolved the basement heating issue, but as part of the work the technician noted that there were some large issues with the installation, mainly that there was only one pump instead of two, and that there was no expansion tank. He said this likely explained the issues we've been having the past few years. Also said without these components, we are significant reducing the life expectancy of the boiler with potential larger issues occurring down the road. He's suggested adding these components in, but due to the work that's going to be required, it's not a cheap endeavor. Was hoping to get other people's thoughts to make sure this is something we should go ahead with, have attached pics of the system here.