Hollman Yes, but mods are in the pipeline for the majority that you list unless they are soon up for the chop. Many have Extended Squitter Mode S or Mode 5 that just needs wiring to the GPS. As ever, sounds easy but is expensive...
Also, your ADS-B emission may well be rebroadcast on JTIDS/Link16/MIDS as a track, so others may well see you that hasn’t been listed. The good news about these datalinks is that they are ‘nodeless’ and don’t need to rely upon ground infrastructure to share their combined picture between aircraft. So you may be quite surprised who can see you.
The bottom line is to poke out Electronic Conspicuity that is ICAO standardised and not from the ‘explosion in a Maplins shop’ devices that BEagle has described. It sounds like
ETOPS has the best idea in using a Mode S to give ADS-B Out but using Pilot Aware for ADS-B In. Although there are cheaper amateur built devices like Stratux - that could cost you less than £50 with no subscription to receive ADS-B. I’ve used SkyEcho and it is good for a low power ADS-B device for transmit and receive, plus also for £20 a year you can buy a licence to de-encrypt FLARM on it too. Completely standalone and no massive antennae like the others - it’s about the size of a fag packet with an 8hr internal battery - also, less than £500, so definitely my choice for now. I even took it for the Rapid Capabilities Office to have a look at.