My veteran agents have turned out to be excellent. For whatever reason, for example they might end up having higher STR than my other agents. But I have not analyzed where (which commendations) this comes from. Once you can get veterans, you pretty much can stop buying rookies (except for buying 30-40+ hybrids for to get bunch of >80 PST for psionics).
I think my highest strength agent right now was a Gunner type request, looking at their commendations rocket scientist, canoneer, jungle mower and gunner medals all give strength bonuses, I dont use those type of weapons much so I guess I should try to in order to increase all my agents strength a little, that seems like the biggest benefit to me that they can come with medals I don't usually remember to work on so it is effectively free bonuses no other agents tend to recieve. Focusing on earning varied medals is probably one of the things I should try to improve on since my usual playstyle is snipers and popping in and out of cover to shoot, should try more heavy weapons and grenades etc. but they tend to cost more / destroy items on floor but it would be fun to try the miniguns
I never did use many hybrids my first time playing but might try this time, the energy and self stun of psi weapons tends to put me off trying them and the hybrids seemed to have low strength if I remember correctly, but the free shield and psi bonuses would be nice if I found a good way to use them.
If you want to use the shield, I suggest trying black-ops pistol. Good range, accuracy and speed, and 30 damage with 0-200 % rolls eventually punch through.
I didn't consider the pistol as a main weapon but looking at it compare to the SMG it does do more damage but less shots so might make for a good trade off so will give it a try thanks
But note that I essentially never use shields against cultists myself. At least after promo II (and explosives license) I would not suggest it as a tactic. Shooting most cultists triggers sniper/spotter mechanics and your units are liable to to get grenaded or grenade launched (in addition to blind shotted), unless you have favourable cover. Throw lots of grenades instead or weapons with area effect rather than direct hit.
I never used the shields the first time so trying them this time, for outdoor missions I prefer having both hands free for snipers etc. but they helped in the cramped corridors of the Black Lotus party / EXALT HQ type map, I just tried a second Red Dawn HQ first time with sniper rifles and second time with shield and pistol, it took a lot more pistol shots to down an enemy but with camping in the bunkers and shooting down it seemed more effective than the sniper rifles due to the shear number of bullets being shot per turn even if most didn't do much
Enemies using explosives is my main threat alongside melee enemies, especially with bunching people together into sniper nests only to have some olympic level cultist toss a grenade half way across the map outside my sight range, I always prioritise them if I do see them since its rare to lose people to a few bullets with armoured vests but explosives and melee can often 1 shot still
Melee is essentially waste of time for the first 6 months of the game due to poor agent MELEE stat. Once you get decent melee stats, combat knives and kukris are both good, as well the stunning options. I usually end up using kukris. But note that combat knifes are concealable, sporting and beach gear, and kukris are none of those, so you may need to keep both to deal with all the mission types.
I've mostly been using melee in my quick change or belt slot which is why I like the 1x2 weapons to quickly pull it out if I end up in danger, I feel like I *should* try the katana etc. but maining melee is a scary prospect even if its powerful. For some reason I ended up using Baseball Bats for beach missions since its one of the few weapons they let me take which seem to have a decent chance to 1-2 shot people to take their guns
You can definitely sell all the veteran agent acquisition rights you obtain, you're not forced to claim them.
I do like the idea of selling them back, but a good agent is worth the money and manufacture time for me, outside of worrying about if there was any downsides to it I also like the idea of fully molding my fresh agents so getting the free medals did seem counter to that but usefulness is better so I shouldnt complain that they come out with useful extras