HVAC recommendation for 3rd floor (attic) unit, poorly insulated

[Tyler Speelman]

I have a heat pump that needs to be replaced.

Residents currently have window AC units, but have complained that it is not cool enough ( rarely falls below 78 degrees on a hot day)

No complaints from residents when heat pump worked. 

Mitsubishi multi zone HP 24,000 BTU + 2 wall units install quote is $7,445.10, approximately $1,000 less for electric baseboard heat install. 

I am getting two other quotes from HVAC companies and have yet to hear back.

Would you do the less expensive electric baseboard heat with separate Central AC unit or go with the Mitsubishi mini-split for AC + heat or would you consider getting a quote for extra insulation (not sure if there is an easy way to blow it in)?

Any advice would be greatly appreciated.