In so far as the independence had been more or less conceeded in 1912 and the Home Rule Act, passed on 18 September 1914, it could be argued that 'independence' had already been won in principle before the 'war' started.
Of course not everyone wanted to be independent of Brfitain, and the Uster Volunteers were formed spcifically to oppose the breakaway, whilst the IRA were all in favour, so long as they were in charge.
Rather than an extended war, a very much more likley POD would a north/south split after the Easter Uprising in 1916. The Brits could then wash their hands of the south, leaving the various factions to fight it out in Dublin for control, whilst a fortified border was constructed seperating north and south, thus making it hard for the IRA (and any troops they managed to convince the Kaiser to lend them) to invade the north.
Certainly, it's hard to see why the British would want to waste a decade of effort fightng an unwinnable** war for control of a country that lacked any vital industry (except, perhaps, the shipyards in the north). Ireland has few mineral resources, no oil, not even coal. Nor did they have massive rubber, coffee or cotten plantations or anything else that might generate the sort of wealth that could be taxed to pay for the military effort of keeping the country subdued.
**unwinnable, that is, without resorting to the sort of methods used by Hitler and Stalin.