Engines - the bolter is irrelevant (although missed approach is not). I may be wrong, but would have thought that on touchdown, the engine will be immediately brought to idle (otherwise you're negating your braking effort) which means if something goes wrong on deck, you have no time to spool back up and regain any sort (wing or thrust-borne) of flying speed off an angle. It's been a while since I checked the distances, but assuming a touchdown point 60-80m forward of the round-down, the size of CVF and probable angle gives you around 120m-ish to play with before you hit the deck edge. At 40 knot relative, thats 6 seconds maximum to get back your rpm, probably a bit less if you factor in things going wrong slightly after TD rather than on it, plus an "oh-sh1t" factor and thottle lag. As if thats not bad enough, if you've done any of the hard braking necessary, your actual speed will be WoD plus about 20kts at best.......
An angle should prevent the deck park having a bad day, but I should have thought we're looking at a very wet and scared pilot and a certain requirement for a plane guard (damn - I knew I shouldn't have mentioned that!).
The STO vs RVL comparison isn't necessarily valid - for a kick off, on launch there are minimal vertical loads on the gear compared to a 3-4 degree glideslope and instantaneous frictional contact with the deck on recovery.
I don't doubt Warton & FW are looking very hard for a safe solution - my concern is that they are looking in a very small box from absolute necessity rather than exploring options for "extra" performance.