Simple, quality brick-clad facades with sash windows, and the optional extra of stone dressings & pilasters etc, are exceptionally cheap compared with any modern glass-clad/ granite-clad/white concrete-clad etc building.
Most, if not all of the bldgs at the north-western end are simple, decorative brick structures anyway, as I presume the Aer Lingus bldg was that used to be on the now derilect site, and the same with Dublin Bus site - Gilbeys being the marked exception.
The RDH, aside from its nasty projecting gold aluminium windows - its brick cladding, as a material, works well in the context of the whole terrace, whatever about its colour & quality.
I think that any material used, other than brick or quality cut stone (to reflect the AIB next door) in the 'refurbishments', will invade onto the terrace.
Remenber, even in the progressive 30s, the Carlton was still built in a classical style using traditional materials to fit into the street, albeit an interpreted classicism, and works really well.
One positive aspect the RDH's redvelopment is the hotel's expansion, which should help increase trade at the northern end. It is planned to add an extra storey to the building, although it will be set back from the street parapet line and invisible from st level, the whole entance lobby is to be gutted, as is I think its coffee shop, and as far as I recall the plans include a whopping increase in its bedroom numbers.