I'm running a homebrew heavy campaign that, ideally, would support characters gaining feats that let their ability scores go above 30.  Obviously this isn't supported in the base rules, but I would hope the homebrew options could support this.

However, when I make a Feat and give it the property of increasing maximum ability score by 50, the character still caps out at 30.  Is it possible to get this fixed?  It seems very reasonable that homebrew content should be able to bypass this core D&D rule as it's (hopefully) a relatively simple backend change since you already support increasing the max ability score and would just need to remove the cap.

The primary purpose of D&D Beyond is to facilitate the rules as written. 

The rules have the hard cap of 30, so the sheet has a hard cap of 30.

While homebrewing can be done, there is a limit and this limit is deliberate.  Given that 30 represents actual near-god-level stats so anything higher would be actual Gods, and PCs that become Gods should now be NPCs (D&D is not the system for "godplay" , it's hero fantasy), there is extremely unlikely you'll ever need higher than 30 in a stat. If you're in a game where you're needing it, and are basically playing godthings, you're probably better off switching to a different system. This is why it is extremely unlikely D&D Beyond will remove the cap. At least not for a very long time. 

If you must play godthings and still want to play it as D&D, then you're better off going to a homebrew-friendly tool, like Roll20.