Just got off the phone with E*Trade and learned of a more efficient way to switch to a cash account as opposed to waiting T+2 for your latest purchases to settle then shutting off Margin. (If you buy any shares from the Margin acct before it's switched to CASH only, you'll be resetting the T+2 all over again!)
Solution: You can open a new CASH account with your broker (E\Trade is who I talked to in this case)*, and transfer your settled shares from your Margin acct to the new CASH acct. Automatically stopping your (settled) shares from being lent out and you'd have no delays if you chose to make purchases from the CASH acct as soon as you'd like. Then when the unsettled shares in your Margin acct settle, transfer them too. This way, you'll still have a Margin acct available to you if you're so inclined, but your GME shares will be safe and unable to lend out in your new CASH acct!