Being the issuer and the exchange was my original plan.
This "underwriter" concept is part of an attempt to convince me to actually allow entities other than me aka my own Corp (Digitalis Data Services) to issue assets on my server (aka exchange).
Even in the game context it is not the issuer and the exchange that would approach being one entity but, rather, the exchange and the underwriter.
That is, since the underwriting can be proposed as a for-profit business in itself, the exchange could have an underwriting department attached as an additional profit-centre if it chose. Or, possibly more commonly, the exchange and the underwriter would be long term associates, a symbiotic relationship, profiting together in the business of helping Corps to "go public".
It also interestingly creates a moat or barrier in that an ordinary commercial loan would be a cheaper way of raising capital; I admit I am still puzzling out why a Corp would go public via an underwritten IPO instead of simply borrowing money without involving the public. I suppose though that the lure is the possibility of raising far far more capital than the nominal "IPO market cap". That and, of course, the prospect of in effect having a "currency" of your very own to play with.