You must clarify with the building authority whether a new development of the same size is possible after demolition, or whether building and planning law complications arise due to the loss of existing rights. For the construction project, you need an architect (building application, possibly a preliminary building inquiry) and a structural engineer, possibly a surveyor. Demolition above a certain size (in NRW 300m3 gross cubic content) must be approved by a demolition application and carried out by certified demolition companies with proof of disposal. Depending on the construction age, the bungalow may be special waste from the regrettable era of prefabricated houses of the 60s/70s.
Your basic considerations regarding the choice of materials are contradictory: bricks with high bulk density have a low thermal insulation value but provide good sound insulation. The heat storage capacity of a building material plays a minor role in our latitudes and has nothing to do with the thermal insulation value/thermal conductivity of a material.
You therefore have the choice between an external wall construction with high bulk density (brick / calcium silicate) + additional ETICS or a monolithic aerated concrete (porous concrete/high-hole brick) at least 36.5, preferably 42 or 49 cm without ETICS, but with poorer sound insulation. Depending on the location of the plot and external noise levels, this construction may not be sufficient.
Furthermore, the Energy Saving Ordinance applies, which defines the energy standard (final energy consumption / transmission heat losses / primary energy demand) of a new building. This affects the choice of heating system, which must be matched to the shell as an insulated building envelope.
Building has become more complicated and more expensive.