I am interested that you say that, because I'm finding the 2.0 corebook advertises that it can do the things you say regarding finally melding personal, vehicle and spacecraft combat but struggling in actual situations.
Would you mind expanding some more on how you use it and how you find it in these situations?
I dont use either book tbh I bought and then sold both of them. I am only using 2nd edition stuff now. The core rule book has everything you need other than for the Merc organisation and mass combat.
If I was wanting to design a Merc outfit at the moment I would probably use CT Book 4 for the organisation and any mass combat etc and I would probably make up my own system for the combat resolution which would be along the lines of players being part of a Section or Squad and they would see only immediate combat situations around them using the vehicle, artillery and fighter rules house ruled if necessary depending on the players desires on what bit of the unit they want to be a part of.
I wouldnt bother resolving the rest of the war much other than passing on briefings occasionally, but if you want to then Book 4 has everything you need to enable that. Again the ARMA2/3 games are perfect examples of what kind of immediate combat experience and the intermediary briefings should be like for the players - ie fast frenetic and confusing combat interspersed with very vague briefings and with the odd plane. helicopter and tank involvement thrown in to surprise them.
I honestly cant remember what the Merc books for Mongoose Traveller were like now but wasnt that impressed with them but then admittedly I have never been that interested in Merc combat in terms of the vague massed battle resolution that they protray. And tbh I dont think players would ever be very knowledgeable about that stuff either unless they were a colonel or general and that would be a rather dull game for them.
Far better for them to be grunts with no information other than 'take that hill' or 'hold this junction'.
I would be very interested in Mongoose covering a more detailed massed combat system along the lines of running a sort of high level hex type wargame where the referee is controlling a series of large combats over a theatre that he generates the results for and they are used to create a real war on the fly around the characters that ebbs and flows in a realistic manner. The referee could generate the results of this war in between play sessions and use this to create small conflicts for the players and inform player briefings. But it would be rather complex and need to cover combined operations, supply, reinforcements, politics, etc. I think it would be a big undertaking but there may well be a simple board type wargame that would be suitable for doing this already I dont know.
But AFAIK no Traveller book has ever done anything like this - possibly one of the CT games has like maybe the Fifth Frontier War game or Imperium maybe. CTs Striker went into this sort of thing but it was too small scale to be really interesting to me - it didnt cover the high level combat resolution. Whereas the highly generalised mass combat in the MgT Merc books was too vague to be really interesting to me. Too much work for the referee to make that into a real ongoing interesting war.