By your definition, all problems with defined finite solutions are effectively solvable. Just set the algorithm A(P_i)$A(P_i)$ to be "output x"$x$", where x$x$ is the solution to P_i$P_i$. For example, the algorithm you would use to solve the instance of IS_PRIME on 37 is "output yes."
Now the algorithm picking algorithms to apply is uncomputable, but you said you didn't care about that.