Increasing the Number of Swarm Units
My first change involves packaging troop units as add-ons to monstrous creatures or elites choices, where MCs or other powerful units have the ability to purchase a squad of gaunts or something similar to accompany them. The can either take up an FoC slot or be tied to the 'purchasing unit', I'm not sure which would be more balanced. For example increase the mawlock to 160 points and give him a 10 gaunt unit included, or keep him the same cost and allow him to purchase x gaunts and y cost to go alongside him. In order for this idea to be worth anything, they will come with a nice bonus: biomorphs purchased by the 'parent unit' transfer to the gaunts, free of cost.
It could be a problem if GW forces you to take a unit of little guys with every big one you field, or vice versa. I feel like it should be a unit upgrade on the big monster. 'you may add up to x hormagaunts at y points per model, these share all biomorphs purchased for monster z' would work for this as an optional upgrade, and could cause the biomorph upgrades to confer to the unit free of charge. You could even paint them all with corresponding shell markings or something similar to make them look like spawn-sisters, and that gets me pretty excited.
Poison Proofing the Nids
Additionally, and as a Dark Eldar player I hesitate to suggest this - I think they should have an ability to purchase an immunity to poison upgrade. Either have certain units/MC's unable to be affected by poison, or have an upgrade available to some units that means all poison weapons only wound on a 6+ or something like that. It's a litle ridiculous to say that the Tyranids are the galaxy's (universe's?) premiere evolutionary force that can adapt to any obstacle, and yet their mammoth bio-constructs can get crippled by a splinter rifle in the hands of a kabalite warrior. It speaks to the efficacy of the deadly toxins in the 41st millennium, sure, but it isn't scientifically sound. Then again, what part of this game is?
Assuming one splinter shard carries 1 unit of poison (which is this case should be venom, but that's a whole extra story), it would be some equivalent dose able to increase the bloodstream concentration of the poison by some amount. At a certain level, it would be fatal to a certain organism based on a number of factors: ability to metabolize the chemical, presence of receptors or targets for the chemical to act on, damage that each molecule can presumably do to the organism;s system, and the SIZE of the organism. The bigger something is, the more of the poison it would need to have in its system to have the same concentration, and therefore the same effect. Big bugs simply need more poison to bring down! Consider again the fact that they likely have evolved some kind of biological countermeasure and it's pretty clear that they shouldn't be wounded by poisons on a 4+ across the board.
This single change could make Tyranids competitive again in some matchups, whereas right now I can just spam splinter weapons and rest easy knowing I have a very high chance of winning the match on kill points whenever I face tyranids, regardless of what I do. This is particularly true if my opponent's lists are heavy on monstrous creatures. Giving this biomorph option to even a select few bugs in their codex could make for worlds of difference in competitive outcomes - and nobody really likes rock/paper/scissors hard counters in this game anyway.
What do you think of these ideas? How do you propose Tyranids get changed in their next release?