It dosn't matter in the slightest what type of modern building fills this in, by definition a modern building on this scale will change the character of the area from Georgian to - well, something else.
Whether it is a sweeping glass clad structure or something clad in copper or polished granite, it matters not in the slightest if it is 'sympathetic' or not. If any modern building was to continue on this site, it should be the existing facade (which was designed not by Sam but by Arthur).
It relates to the street excellently, as do the materials used (excluding the horrendous ground floor)
Here comes the but.
I think the house facades should be rebuilt.
For one reason only, to restore the unity of the area, and not just Fitzwilliam St, but the whole Georgian character of the area.
I remember as clear as anything the first time I saw this building - it was the first time I walked around the Georgian city, an area completely alien to the rest of the generally shabby and incoherent Dublin.
I was bowled over by the manner in which no matter where you looked, there were Georgian houses lining the streets, from Merrion Street to Merrion Square, to Mount Street and then - the ESB.
And contrary to what someone mentioned earlier about the building acting as a good orientation point, I found it had the exact opposite - muddling - effect, it was like I had exited the historic area, the junction with Baggot St further confusing matters and the unity of the area was lost.
When you come up from the Green through Baggot St, past all of it's Georgians, you arrive at the junction. Look left - more Georgians. Look right - aggregate concrete. The area is destroyed.
And the route from Merrion Square, also taking in the Mount St vista, through Fitzwilliam St to the magnificent Fitzwilliam Square and further on down to Leeson St is also wrecked - with the ESB plonked mid-way, disrupting the whole flow and ruining the continuity.
The basic point is that Dublin's Georgians rely on each other for effect, to create the 'massing cliff' formation. And each street relies on it's neighbours to unify the character of the entire area.
Rebuilding the facades (not interiors etc) restores this unity and character.
At this stage its nothing to do with history, harking back, the British or anything else.
It is about architecture, and the architecture of the area in my opinion would be greatly enhanced with the reconstruction of the 16 houses' facades.
If this Geogian core had been built 5 years ago, most people would see the logic in unifying the area.
But most discussing this issue get what is essentially an architectural issue mixed up with the usual issues of being revisionist, harking back, colonialism, what is Irish etc etc