I guess the thing that bothers me the most about rituals is the cost of components...They seem prohibitive. Why would anyone go to the trouble of purchasing the reagents to brew a potion when you could simply buy the potion (assuming you are at a market that has both available)? If buying the parts to install new brakes for your car cost the same as having a garage install new brakes for you, who would ever buy the parts (and how would the garage ever make any money)?!?! If you go to the local shaman and ask him to sell you a potion that cost him 50gp in components to produce, why would he sell it for 50gp? Maybe I'm misunderstanding?
So I think house rule number one is that the "Cost" for a ritual is not the component cost, but the cost to have some NPC perform the ritual (so for an NPC to brew you a healing potion costs 50gp...). The cost for components to peform the ritual yourself will be considerably less. I lean towards 1/3. Will this break anything?
House rule two is that if you have training in the relevant skill, you can perform its associated rituals.
I also intend to start including in treasures, components and ritual scrolls.