Of course, the trains would almost certainly be busier if there were stations at Abronhill and Bonnybridge. Urban areas these (probably relatively lightly loaded by comparison with the E&G) trains to both of Scotland's largest cities will pass right through...
Both would certainly be welcome in my eyes. Abronhill would give a 4th option to Cumbernauld which may help to spread demand as some have suggested.
Bonnybridge would probably have the best business case on the line as it also serves the wider area of Denny, Dunipace, Banknock and Haggs etc. It also (I’m not too familiar with the area) would have the possibility of being located just east of Greenhill Upper Jn which would probably mean being served by the Glasgow-Stirling/Alloa. A 4tph Glasgow, 2tph Edinburgh and 2tph Stirling is a perfect business case for the station.
Winchburgh also deserves a station, I’m not sure how far the progress is with it but I’d hope it’d open soon. A rapidly growing village/town but would likely only be served by 2tph to Edinburgh and a long roundabout way to Glasgow (2tph). So it probably isn’t as strong a candidate.
These probably make the long E-G via Cumbernauld even slower, but oh well.