Indeed you can gift suits and helmets. I think I gifted 4 of each from one account and proceeded to gift as many as 2 more of each from my main account. (I think I tried to send more and it gave me the daily limit message) That's a total of 12, on top of the normal gifting. I may be misremembering.
Also, I really like the display of weight distribution. I always wanted that to be included in the settings. Unfortunately, on a 1200kg car, the 200kg doesn't make a big % chage front-rear, maybe 5%, if you add the whole weight, which is bad. So my fully lightened Supra RZ with weight distribution of 60-40 can't be helped much. Also, the Supra doesn't look any better than it used to. It's one of the poorly finished cars in GT5.
So far, I saw you can buy parts in your settings area, but not unreversable mods - engine mod, weight reductions.