So you're looking for an agent to do paperwork for you. You should just hire an attorney to do the work you want done. Here's why:
1. if you think that it will get expensive for you to keep having an attorney write offers for you that will not get accepted, then maybe you should write offers that are reasonable. If you think that any agent, whether the so-called discount broker or the "full price" agent, will keep writing ridiculous, low-ball offers, then you know even less about real estate than you sound like in your questions on this site.
2. If you find an agent who will work for less than the amount offered as a co-op fee, that agent is a fool. The remainder of the commission that the agent does not want to earn will be earned by the Listing Agent, as the Listing Agent has the contract with the Seller for the commission, not the Selling Agent.
3. If you call a Listing Agent to show you the property, then he/she has no obligation whatsoever to compensate another agent who helps you to write an offer on that home. It's called Procuring Cause, and the Listing Agent, being the Procuring Cause on the home is entitled to the commission for the Selling side of the commission as well as the Listing side of the commission. So really, the way you want to do this will only get the discount broker no commission. If you did this to me, as a Listing Agent, I would be sure that the other agent's Manager/Designated Broker know that the agent was infringing on my Procuring Cause. I would make sure that the deal would close, as I wouldn't damage the potential sale for my Seller, but I'm sure that the agent you selected would have walked away, knowing that he/she wouldn't be getting paid.
4. If you don't want the services, then tell the Selling Agent who you're working with that you don't want his/her advice. He/she will, if the person is smart, have you sign a disclosure that states that he/she tried to give you advice about the transaction and you refused to take it. It's called covering yourself. I wouldn't take on the liability of you potentially suing me (as people like you are apt to do when you make a mistake) for not giving you good advice.
5. Back to hiring yourself an attorney - why wouldn't you do this? An attorney will do, or not do, whatever you tell him/her. That's your best bet.
I wish you the best of luck in your search, but I really don't think you'll have much success. No agent wants to have a client who wants nothing better than to screw the agent out of commission that he/she works very hard for. I sure wouldn't want to deal with it. And before you get on your high horse about how selfish and greedy I am, I donate much of my time and money each year to charitable causes, but they're causes I choose, not clients who squeeze me.