Things like this have been done before. For example, DSA used to offer a partially railed, top cover with integral stripper clip guide for FALs. The M-14/M1A comes stock with a stripper clip guide, although this must be removed if mounting a conventional scope; a conventional scope on either an M1A or Garand, especially, being a mistake, IMHO. Even the Mini-14 used to have available as an aftermarket part a stripper clip guide that attached to the threaded hole on the side plate cover. One could sight-through the stripper clip guide, and it also offered some protection for the rear sight if the rifle was dropped flat onto a level surface, such as the typical firing line at a range. Granted, rifles should not be dropped, but........
The reason for these things existing is laws that prohibited rifles with interchangeable magazines. The user would disable the mag latch in some manner, with mag of any legal size installed, and feed it from the top via stripper clips.
Such devices might see a resurgence if more States enact draconian gun laws. Some firearms owners might consider buying such devices ahead of time in case their State enacts certain anti-firearms laws. Of course, diligently working with others to prevent such laws is the best action, but buying these things is not only a decent backup plan, but allows the mfrs to continue making the items. For example, as an artifact of the original 1994 Assault Weapons Ban, the Mini-14 has (fortunately) not received the attention of the Antis which it actually deserves. Same thing with the Garand. Perhaps on account of that fact, the stripper clip adaptors are currently not to be had. I don't know if DSA still makes their stripper clip top cover for the FAL.
With the Trump administration in power, we are unlikely to see much in the way of Federal anti-gun laws, but as some Members can attest, some States will pursue their own Anti-gun paths. Witness NY, NJ, MA, CT, CO, and others. The Antis seem to be focusing on State legislatures, in lieu of the FedGov, because they can be bought, and for cheap.
As always fighting such anti-freedom laws is the best defense, but I advise having a Plan "B", just in case. YMMV.