In computational chemistry of transition metals, there are many popular basis sets, from pople+LANL2DZ mixed basis sets, to Ahlrich and Karlsruhe basis sets like def-SVPD, def2-TZVPPD. Often the ECP versions of these basis sets were used to minimise computational expenses. However there are molecular properties such as topology analysis and energy decomposition analysis where a full electron basis set is not only recommended but also necessary.
One of the full electron basis sets commonly used in the literature is the ANO-RCC basis set. However, such a basis set is so large that it computationally infeasible in applications like the EDA2 calculation in serial qchem (where there are no parallelisation implemented) and barely feasible in generating wfx files within hours for analysis. Thus a slightly smaller full electron basis set (if any) is needed to be selected.
Say I start with some ECP basis set X, which I can read the list of all exponents and angular momentum functions used, what is the recommended approach to upgrade it into a full electron version of it so it retains most of the properties of the original basis set while making it full electron. Do I need to perform a benchmarking again and compare single point energies at optimised geometries to be sure?