What is more important: unity of mechanics or the rules working as the players expect?It's about unity of mechanics.
This is why I prefer PF to TB.Actually, spiders and monkeys use the exact same rules for climbing, RAW. There's no functional, mechanical difference between the ways that spiders and monkeys scamper up a blank wall.
You and I both know that spiders and monkeys climb in very different ways. It is fine that the default mechanical resolution is the same, but you are now letting the mechanics control the flavor. The opposite must always be true.
Nope, there is a very important difference.The spell also already works as Valhalla described, and pretty much as I intended. (Haven't read it in a while.) It's already better cast on a rogue than a wizard.
"it need not make climb checks to traverse a vertical or horizontal surface (even upside down)". No checks required.
And honestly, whenever I've had a spider in play, the same system has been in use for them. It appears I have been house ruling that one, but so be it.
You can cause a monkey to fail a climb check. It may be difficult, but it can be done. I suppose some form of Bull Rush type effect could swat a spider off a wall, but it will not fail a climb check.
But the creature conversation is a far tangent anyway. Go up to a non-gamer buddy and ask them what it would be like to climb like a spider and also ask them what it would be like to climb like a monkey. You will get different answers.
Quit letting the rules use you.