thou you have good intentions, I'm not so sure it would be a good idea, the embassy might get suspicious of how you can be the father when you wasn't in the phils or didn't even know her then, they could ask for a dna test, and i wonder if the embassy would say that your using fraud to obtain a visa if found out, and the child/mother could face a ban from coming to the uk..
i think it's better if the baby is not registered to register the child and leave it blank where the fathers name is, then you shouldn't have a problem obtaining a settlement visa for the mother and child then.
but maybe a filipina would have a better idea if what you want to do is legal in the phils i doubt it is thou
get her here, and then you could try adopting her or she can change her name when she is older by deed poll. i didn't bother trying to change my stepsons surname, end of the day i am his step father. and i thought it better he keep his family name.