Okay...
I have been re-reading the thread too. It has got a bit confusing. Emily's MC and Alexander's DC I think closed a lot of holes and gaps...in that I believe that the father is one and the same. Does that make sense? There were too many connections...ie, the rank (fishy or not!), the George Patrick etc.
You said there was a regimental birth, Monica, of Isabella, and I think that one might be worth getting...because I do think, Isabell was baptised later than all the others...I checked with my mother in law today, and the "Sponsor" can be anyone who has been confirmed...which means I think from the age of about 11 or 12. This would fit.
yes, McGrath does throw a spanner in the works...but I'm leaving that slide for the moment...
So, If Isabella was born in 1849, Caroline could still be out there, and other's...
Elizabeth's middle name Frances is a bit odd, hasn't turned up anywhere YET!
Andy, the other confusing bit, is that on the birth record of Emily, the address is down as the Clonmel Barracks, but Alexander is retired, a pensioner...why would he still be living there? Could he have re-joined?