Good question, or perhaps more pointedly is there the funding for such extra channels? - especially TG4.
When the multiplexes were launched (the platforms on which the channels operate), RTÉ was given a whole multiplex to itself enabling it to have up to about six channels in total (incl RTÉ 1&2), while TV3 and TG4 were given half a mulitplex each meaning in theory they could probably have two extra channels each, but one is more likely. In any event, it's best to keep the number of channels per multiplex to four or five to reduce the amount of compression required. This is a problem in the UK I believe.
RTÉ's original proposals way back in 1997 were for a news channel, an educational channel, RTÉ Plus showing RTÉ repeats, an Oireachtas channel, and a channel possibly dedicated to local and regional access television.
By 2000 or so this had morphed into a 24 hour 'information channel' - presumably with news at its core - called 'Ireland Today', a young people's channel called 'Zap TV' (I know, it gets worse

), and a learning and education channel called 'Eolas'.
Whatever about the names, I can still see this package being rolled out today, presumably with 'Eolas' also encompassing repeats - RTÉ does have a
vast
archive that needs to be put to good use.
RTÉ Three and RTÉ Four should definitely be used as branding - remembering the RTÉ Branding Blitz that we so know and love today hadn't been invented yet way back in 2000
I think RTÉ News is enough as a branding for a news channel - what do you think? If it included other material though, it may need a broader name.
The thing about parliamentary coverage is that it is incredibly cheap and fills up vast quantities of time, so much so that it's really unsuitable for use on a news/information channel such is its sporadic nature and its eratic durations. A channel all to itself is really required, remembering that everything from Dáil sessions, to Seanad sittings, to Committee meetings can and ought to be covered.
At present there is continuous live feed from Leinster House to RTÉ in Montrose, and is probably even partly paid for by the Oireachtas, not sure, so either way it costs pretty much nothing to run an Oireachtas channel - just the start-up expenses.