Simmonds will easily return a 1st or something of equivalent value. Boston, Nashville, Calgary, Vegas, Toronto, Tampa Bay, Winnipeg are all the teams that are interested in him some way or another. Competition between teams that will play each other in the 1st or 2nd round will attempt to outbid each other.
The saturated market assumes that everyone will be traded. Ottawa is playing chicken with the rest of the NHL. They can't afford to get anything less than top value for their players. There is no guarantee of Columbus trading Panarin. So even if you keep Duchene, Stone, and Panarin in the mix, Simmonds is like 5th best in the scope of being traded.
If Nashville doesn't want to pay what Simmonds is worth, then Vegas, San Jose, Winnipeg, of Calgary could. Can Nashville really afford to sit on their hands while other teams get better. (Example not just directed at Nashville, but all playoff/Stanley Cup aspiring teams)