I agree with Gary and others that I think it is too late for whoever markets DCS to keep producing the traditional TIU and remote technology. It costs companies money to keep producing older technology. However, I will answer John's initial question; I would purchase one TIU and remote if offered. I had been thinking of purchasing a spare TIU for my 11x11 layout room, but didn't do it before they were discontinued. I did get a spare remote in this last batch that were produced. I tried the WIU when it first came out, but didn't like using the phone touch screen. After a couple years, I sold the WIU to a Forum member.
All that said, I certainly wouldn't have an issue plugging the remote into a WTIU in such a small room as I have. That may be the route I take as long as I have remotes. Push come to shove if I outlive my remotes, then I'll go back to a touch screen on a phone or tablet.