I would still suggest something like plug in modules for RX. These RX modules could be optimized for certain bands (VHF low, VHF-hi, MilAir, UHF, 700/800, etc.) Maybe have additional Ant ports for each RX so you would have a matching antenna for that band or a simple bypass via a jumper to utilize a common ant.
Also FTO could use the additional RX so that while normal scanning is the going on a second RX could be set as priority for FTO.
I'm sure there are a few that currently use FTO, but I do not because I don't want to tie up a scanner to just act as a pager. In practice, this scanner would act as a "normal scanner while a secondary RX would monitor FTO. Once the proper tones in FTO are received, it would sound an alert tone and play the paged traffic.
MDC1200 and the other flavors decoding. Yes I know there would have to be royalties paid. I would guess that the royalties would be low being how old the tech is, but that is just a guess on my part.
Add built in GPS (Sorry John). On the mobile/Base model, it would add a small antenna "hump" around the size of a xm/sirius antenna (Smaller or no hump would be better), but also allow an external GPS antenna connection on the back. Dump the multi wire setup that is currently offered for GPS.
Remote Head capabilities. With newer vehicles, space available always seems to be a challenge. Remoting the head seems to be a constant wish of many I see here in a mobile environment.
I know personally, in a mobile setting I prefer remote head style, even in my charger. All my remote radio main units are in the truck behind a metal protective cover. I can keep my coax runs short. Power is right there so no long runs for power. Honestly please consider remote head possibilities. Use Cat5 cable between the head and the main unit. In my RV, again I have a dedicated space for the main radios to live while the heads are located in a convenient/safe area.
Lastly, dustproofing/waterproofing. So it could be in car, truck, dirty dump truck, boat, etc.
All for the low low price of 29.99. LOL
(Flame suit on)