Yes, I'm planning to only run on electric. I have everything to run a RIMS setup but I decided on that when I thought I was going to do the Brutus 20 style setup with two vessels. I've since decided that I wanted to do the whole 3 vessel style brew rig and I like the HERMS style as well.
I too love designing and building these sorts of things which is why I'm really enjoying this process. I think I'm going to design my control box to be capable of doing both RIMS and HERMS since im only needing the HERMS coil at this point to have it as well. At least this way I will be able to try both and decide what I like.