>>>>>well it took me so long wiriting this .... just look at the post above mine^^<<<<<
ok, first i would not just remove the spells, but try to replace them with a dummy spell. One way would be using a version of the spell that needs a tech-uprade that the player will never have, so the spell 'is still there' but not usable, or replace it with a passive spell that has no effect (e.g. 0% evasion) but the same tooltip and icon as the original spell.
For items i would suggest to check every item slot of the hero (with triggers, 'For every Integer A (1 to 6) do....' for example) if there is a item that grants invis in any way and replace it the same way as abilities (you will have to somehow save every item you replaced). Either you check for every type of invis item, or you check on pickup and give all items that grant invis the same 'custon value' via triggers when they are picked up and then just check every slot for a item with this custom value and then replace them it needed.
But please know that I'm not experienced with triggers so maybe someone else has a better idea