Like it or not, that's the way I see most fire alarm projects bid - design by the contractor. That's also the way most fire protection contracts are bid.
How would I know if a panel needs an expansion module? Most of these existing installations look like crap with wires hanging out and everything else imaginable. I wouldn't dare touch it, much less open a cover and try to decide if an expansion module is needed. My only hope would be to ask the person who has installed and maintained this mess, who is basically going to be one of the bidding contractors. His incentive to be helpful is ziltch, and he is free to lie all he wants. And if I asked 5 different people, I'd get 5 different answers, and whoever got the contract would still come up with some off the wall request for a change order for a needed upgrade or recall, or some other made up reason to ask for more money.
I see electrical contractors work their buts off for a bid, but it seems like its too much trouble for a fire alarm person to even visit the site?? And fire alarm contractors usually have an inside track based on the existing brand of panel- the manufacturers limit the number of competing contractors, or it may even be a single sole source contractor with no competition.