Not really. Rebreathers are finally coming around full circle. Now they’re simple again.
No electronics. ADV’s are generally removed. And oxygen solenoids are set to a minimum level, on eCCR’s so that they never kick in if the CCR is being controlled manually, properly. eCCR’s are obsolete.
mCCR’s with a needle valve have surpassed the eCCR. Especially in reliability. The electronics on an mCCR are just there to monitor the O2 levels, and apply them to a dive computer. It doesn’t control anything.
mCCR like the Fathom mkIII are the future. I’d suggest that you certify and master one of those before building your own.
Hopefully I’ll be able to switch over to a Fathom CCR in the next few years. Have to do all the nitrox and trimix, deco training first. For now I’m after longer NDL’s, quicker deco’s, and free custom nitrox. I won’t be cave diving.