Walker had some nice touches against Catalans, but looked a bit exposed when some of the high kicks went up. His form has been up and down this season, but unless he's injured I don't think it's fair to replace him with Lolohea.
Assuming this can be worked in terms of interchanges, Lolohea might be useful as a sub to cover a number of positions in the backline and inject something different in attack if needed. But then we'd probably have to go without one of Dwyer/Parcell, which might nullify other attacking options.