Advice? Favorite Biocube 14 upgrades

Been out of the hobby for awhile and not really sure what the latest and greatest improvements are. Looking to upgrade a Biocube 14 from PC to LED lights for LPS or even SPS capability if possible. What are your favorite prebuilt or DIY kits/retrofits? Would prefer to fit it in the original hood. Got any other possible improvements: mini skimmer, flow, etc? Would love to put a sump under it, but don't want to drill the back and risk a crack.

Planning for the end setup to be able to exchange water with my main display tank in lieu of a traditional water change, so water quality is less of an issue

 

I've still got my Biocube 14 though. Its going to be a frag tank i think.

Fun fact about this actually: all my corals were pretty much dead, the lights were burning out, I was burning out...so one day like 2 years ago I just unplugged it and left it as is. A few weeks ago i was moving it around and peeked inside. With NO incoming nutrients, lights, flow, heaters, or water changes/top off, the bristle worms, mini star fish, and mini snails are still thriving! About 50% of the water has evaporated out by now, so I imagine its completely toxic to anything else