iMessage is only most beneficial to you. Since you have friends and family members with iPhones as well. But iMessage is only going to work as well as the phone.
iMessage can malfunction and then send your iMessage via text message. Which I'm sure you've had happen before--being and avid iPhone user. iMessage transmits via Data only.
Why would you want a limited messaging plan anyways? I don't know of any carrier that has a limited one and if they do I'm sure they provide you once of those nice analog phones.