This is a satellite Map of Paisley includes the proposed rail link which includes a viaduct over St. James Playing Fields and the M8 motorway before heading into the airport. As shown here there would need to be demolition of some of the local industrial units to make way for the new spur if it was to be exact route. 

Photo Credit: SPT

Here’s a computer generated illustration of what the proposed bridge over the M8 motorway could of look like once it was built. (From the PC Game: Train Sim Classic)

The 2016 Tram Train Proposal was to avoid the most of the the playing fields at St James.  According to this Map from the Traim Tram proposal video.

Photo Credit: Glasgow City Council 

In 2022, the concept of the Clyde Metro was announced as part of Scotland’s second Strategic Transport Projects Review (STPR2). The Clyde Metro is a long-term vision for a multi-modal mass transit network serving the Glasgow region, including a potential link to Glasgow Airport.  

The Clyde Metro envisions integrating heavy rail, light rail (tram), and rapid transit modes across Glasgow and surrounding areas.