Running services through the low level is a good idea on balance for stopping services since it means passengers have a direct service to more of the city centre. If you want to run more services into Central High Level then the low level option delivers more capacity for a reasonable cost. Exhibition Centre could be remodelled so that the current turnback siding could become the westbound platform, leaving the centre platform for use as a turnback. A plan to turn the eastbound platform into a central turnback at Hyndland was dropped but could be restarted with ease. Both of these would increase capacity through the low level without affecting the Hyndland flat junction, at far lower cost than the other options available at the high level station. Really, there isn't much that can be done now without the need for major changes, such as tram-train conversion or a full heavy rail north-south tunnel. The business case for either would hinge upon there being no other solution, and if capacity could be found going through the low level, neither would go ahead.
In regards to Exhibition Centre terminators, I do not know if anybody has ever examined the possibility of reopening the western part of the Glasgow Central Railway to Maryhill Central, with reopened stations at Kelvinbridge (interchange with the underground), and Botanic Gardens (the very first railway station outwith the G1 -5 postcode area heading westbound along the A82 Great Western Road (or "The Boulie" - short for Boulevard as it is referred to by people from neighbouring Clydebank) is Anniesland. This would connect Hillhead/Dowanhill/Kelvinside to the railway network, and with the reopening of Maryhill Central, would reconnect that part of Maryhill and neighbouring Ruchill and the Wyndford too.
Of course, there is also Glasgow Crossrail which needs no fancy bells and whistles, as the City Union Railway is already operational between Shields Road and Bellgrove, and the platforms at Cumberland Street are already
in situ with only the overgrown vegetation needing to be chopped down. Also, the island platform at Glasgow Cross on the GCR is already
in situ - the reason why Glasgow Cross station did not reopen in 1979 was (according to a friend of mine who worked in the transport department of Strathclyde Regional Council) because the eastern flank of the motorway box (from Townhead to the southern bank of the Clyde, where it would join with the southern flank from Carlisle to Tradeston and onwards to Greenock) had not been built, and it was intended to use the former platform of Glasgow Cross station to fix concrete pillars to so as to support the elevated motorway above.
As the eastern flank of the motorway box would have meant demolition of Provand's Lordship (the oldest residential building in Glasgow), Barony Hall (part of Strathclyde Uni), all the buildings along High Street including College Bar (believed to be the oldest inn in Glasgow) and the Tollbooth Steeple at Glasgow Cross too. Needless to say, this section of the motorway box was never constructed.
Back to railway matters now, and by reopening Glasgow Cross station as part of Glasgow Crossrail and HS rail, this would regenerate the historic centre of Glasgow. To the west of the Cross, the Merchant City G1 postcode) has had piecemeal regeneration, with some posh flats and posh bars. East of the Cross, go 100 yards or so along London Road and you are into G40 postcode, which is one of the most deprived postcode areas outside of London. Yes, Dalmarnock, Barrowfield, and Bridgeton Cross have had some regeneration recently (attributed to the preparation of the Games last year), but the Calton has hardly had a look in. Also, the Calton has the lowest life expectancy according to a World Health Organisation report from circa 2009, where the residents are not expected to live beyond the age of 56 years. Through the Glasgow Crossrail project, this would help aid regeneration of the areas both west and east of Glasgow Cross.