1. You actually need no LOG in your boarding troops, because there is nearly no chance for boarding combat to last enough that wearable ammo will be drained. You can still reserve some LOGs for possible planetary combat, but it's rather inefficient use of boarding troop space.
2. LB (grenadiers) are useless for boarding too, because there will be no vehicle elements during boarding combat, and if your opponents will have enough personal armour level to tank your PWI - your companies are meat: no chance that 4 grenade launchers will be enough to mow down enemy platoon or decent ship's crew of such tech level. Again, you can reserve grenadiers for possible planetary combat, because it's theoretically possible to meet several armoured vehicles there and your compamy will die helpless if they have no anti-vehicle weapon at all and there will be no reinforcements, but it's rather inefficient reservation.
3. PWI is inefficient in boarding combat against equal-tech enemies, because their main targets will be unarmoured crew members, so no need in penetration, you'll need more shots instead of less high-pen ones. Though it's possible to meet higher-tesh opponents and then you'll need increased-pen mass weapon to have any chance to win boarding action, and higher-tesh prizes are the most valuable ones if you have enough speed and luck to launch boarding action. That's a question of compaign setup and your expectations-and-plans.
4. Doubled HQs for platoon level cannot be usefull enough to be efficient at all; it's doubtful even for company level. Minimal volumes of HQ elements are quite big for those small-size formations, and so HQ redundancy is overexpensive. You have to manually pick up the best of your junior officers to make even single HQ element efficient enough for it's volume, so I'd vote against marine HQ units at all (roleplay-wise you can name your PW unit as an officer and to have 1 such unit in formation, but it's not headquarters unit as such).
5. You have marine heavy (machine) gunner and marine sapper designs, but no such elements in your marine formations. It's wasted research points, though not very much of it.