Are you planning to have electric only?
I have a HERMS/RIMS propane-fired rig. I have all the wiring for my EHERMS and ERIMS upgrades completed. I'm almost finished with the EHERMS upgrade (elements in the HLT and BK). After that I'll finish the ERIMS upgrade (an ERIMS tube).
Having both HERMS and RIMS is a waste of money. It's fun and exciting for me to install these upgrades. I actually enjoy designing and building more than brewing and drinking!
Having both available does allow you more versatility. I think Boerderij_Kabouter said it best:
Originally Posted by Boerderij_Kabouter
They are not redundant at all. They provide distinct advantages and disadvantages that can be utilized to make brewing any particular beer easier. For example, I use HERMS for a single temperature mash because it gently heats and maintains an extremely constant temp. I use RIMS for step mashes or any multi-temp schedules including ramps or whatever the hell I can dream up.