I am personally happy with this "no limit" as I considered in the past this 80-limit was a nonsense
Especially when I tried to load 20 pistol clips and 60 rifle clips, and had also no free place anymore to take any other weapon : this is not as if I was trying to load 80 rocket-launchers...
But I agree this was a constraint that was part of the game and you are right to say removing this limit changes the game balancing
Would it be not more logical to implement a limit in terms of storage capacity (I mean taking item size into account) instead of number of items ?
Right, question already discussed
It surely would be more logical, but this strays ever farther into the territory of "modding."
Another scenario that occurred to me was, with some kind of limit, and the 80 item limit in the main game, there was another strategic decision that came up. With a squad of 24 men, it was generally the case that you knew those 24 men would be spread thin in terms of equipment. You might get, say, a plasma weapon, one clip, and a grenade, with a few more items for spice. However! If you decided you wanted better armed, more elite troops, now there are more decisions to be made. You might purposefully take less men in total in order to better equip those that did come along. This gives the player another reason to use the sometimes maligned HWPs. Or, perhaps you might decide to switch to laser weaponry, specifically to save yourself another 24 items on clips. Now, you've traded some firepower in order to be more versatile. Or you might combine the two, both replacing some men with HWPs, and also choosing to use laser weaponry. Now, you have soldiers that are equipped for a wide variety of situations, but you've sacrificed both pure firepower and boots on the ground (keeping in mind that trained soldiers own HPWs) in order to bring along more secondary equipment. These are the types of decisions you'd expect to see in a game of this type; it's merely happenstance that in X-Com they exist because of an oddly implemented limit on total carried items. I would argue however, that if the nature of the decisions is correct to the game, it doesn't matter that the reason you're making them is to avoid an arbitrary item limit. Really the absurdities only reveal themselves when you start trying to carry 150 rifle clips into battle or give every soldier a half-dozen grenades, three clips, a stun prod, and flares.
The point I'm trying to make in general is, simply removing the item limit wholesale rather than making it more configurable is not quite so obvious a choice as it might seem at first. The item limit had many effects on the game that affected the way one played, and similarly, removing it also has many effects on gameplay, both good and bad.
However, if adding a configurable item limit to transports is too difficult or otherwise not worth the time, perhaps a compromise? A simple counter of total items on the plane in the equip transport screen. This would make it easier on those of us who would like to preserve the kinds of strategic decisions discussed above, whilst not putting entirely on us the responsibility of self-policing item count by manually adding up line-items on the equip screen.