You cant use improved climb if your field limited for starters.
IC uses excess runway to help clear obstacles, this is done by increasing the Vspeeds.
Speeds can be increased up to the point where the field length limit TOW and Tyre speed limit TOW becomes more limiting that the CLB limit TOW. If the resulting V1 exceeds Vmbe the improved TOW must be adjusted.
Due to higher speeds, there is an increased chance of being limited by brake energy (which limits V1) or tyre speed limitations (which limits Vlof, thus Vr). Vtyre might inadvertantly be exceeded by slow rotation.