The point defence weaponry is easier to spot and neutralise from space (a heavily armoured cruiser with a good meson screen and lots of meson bays and or missile batteries will do the trick here).
This will be setting (and the conventions and laws of war on it), as using mesons against ground targets is clearly nuking them (as would be using starship fusion bays, as described in MgT). I may be quite an optimist, but I envison a setting where those weapons are left for space (so, targets outside atmosphere are fine game, inside of it, they are not), out of fear of retaliation.
So, I believe, in this setting, lasers and HE missiles to be the main orillery support weapons (they are quite letal too against ground target, as they multiply their damage by 50 when going to personnel/vehicle scale).
After all, I don't believe the attacker to want to conquer a barren planet (unless it already was, off course

), nor the defender to have it after the battle, regardless it wins or losses.
Then you can send in your drop troops supported by gunships (what is the smallest ship you can get a factor 9 screen in?) to mark the meson site sensors for bombardment.
I'm afraid you think in CT/MT terms. In MgT the meson screens are not rated by factor as on them, but modify the meson damage.
Meanwhile the defender must also use scattered troop deployment to try and counter your drop troops, since any concentration of force or armoured vehicle is an easy kill from space.
Battle dress really comes into its own on this type of battlefield because of its ability to carry heavy weapons as force multipliers against any combat armoured defensive troops.
Once you start to think of what TL15 weaponry does in Traveller you realise the TL15 battlefield is very different from the TL5-8 battlefield...
Agreed in all this
No TL15 world IMTU would have such a gap in its defences...
consider the air defence radar systems that cover Europe and the USA - try and find a gap in that.
You have to make your own gap, which tells the defenders where to move their portable sensor systems, or you make a gap then a gap then a gap and try to overwhelm, or go for shock and awe - make a massive gap and get your drop troops down as fast as possible to allow you to get your own mobile sensor net and point defence in place...
cat and mouse.
This will also depend on the population of the world. Even a TL 15 low pop world is unlikely to have the whole planet covered by sensors and mesons to defend it.
And don't forget about jamming/chaff/whatever it is used as ECM at TL15. it can also help in making the gap you need, even if only for a while...
And, BTW, I remember ceirtain Mathias Rust landing on the Red Square in Moscow...
Someone should have made a game for this...
Agreed here. IE is in a too large scale...