Hi,
cell with wide coverage could lead to sdcch and tch congestion because of big coverage, then sdcch assignment failure, sdcch drop, they all could be the consequencies of that. To much area covered, possibility to interfer and to be interfered is high. To far MSs may camp to that cell, so, possibility for sdcch congestion for MSs near the site, assignment failure for MSs far from the site etc. This is only my assumption, it depends from number of subscribers in the area, number of sites, frequencies etc.
Regards,