The other thing this would do (the highlighting) is make it slightly harder for the issuer to manipulate the price. Because you could see all their buy/sell orders. I say slightly because they could still transfer the shares to an alt account and sell from there, however, as soon as you transfer the shares they become market shares not treasury shares, so it's easy to detect.
Forcing to buy only from one source is not really acceptable imho. If a holder can't place asks, his only chance of selling would be to sell into available bids. They would essentially be trapped and only left with hope that everything goes fine and fast. Buyers could abuse this by placing very low bids and wait till holders lose their patience. There are several more scenarios... but I'm sure, you are aware of the consequences.
I really like the highlighting idea. Not sure about persistent highlights for issuer's orders though. +1 for transparency, but ... well, I'm not sure. Other possibilities would be to only do this for IPOs or make it optional at all.
Fillig a specific order would be very nice feature also. In combination with color highlights this would be very helpful pre-IPO and there are more use cases. For example: if I want to buy/sell into my own orders safely. There should be some limitations in a way that it would be impossible to create a very different impression of an asset, i.e. by pushing 24h high/low or something. To fill a specific order there could be an advanced view of the order book which would show the orders unstacked.