Yes, I also agree. I want to put in my own software, and it can just as well be something external. There are neverthess some considerations, such as picture setting (including backlight controls), volume controls (if you are not using external speakers), input select (if there is more than one), OSD suppress, etc. Connect devices together with IMIDI cables when wanted to program one device to command another (e.g. for date/time synchronization, VCR recording, to transmit captions independently from the picture, to affect volume/input using a unified interface, etc). You could add a separate computer with your own software and then use the existing display, to display its output, and deal with remote control even turn it on/off automatically, or if the display has its own IR receiver, using that to control the computer, using IMIDI to do it either way (IMIDI-over-IR from the remote control, then send to the IMIDI cable connected to the computer, and the computer may send back a command to switch the input or whatever, or forward the command to another device such as a VCR, etc).
If you can use your own computer instead with your own software, then you can program it for the feature you like, such as what I might like to include would be numbered menus, caption scrollback, OSD suppress, etc. This can then be implemented, including the exact way of how you want the captions rendered (font, opacity, etc), the OSD timeout and position, the type of command input (e.g. if you want it like Vim), if you want it to include Viewdata, and everything else you will want.
Since, if it is a dumb display then it will not render captions by itself, nor most of the menus you might use, so you can instead do it by yourself, and it may well be designed better than what everyone else does.
But, well, I would also like a 4:3 display, and without HDCP, and with the possibility to add a full side panel with the channel/mode display separate from the TV screen (like some old TV sets do).