Kerbal Space Program

The Dessert Launchpad and Airfield doesn't have the mass limit check, while the Woomerang LaunchSite and Island Airfield (and obviously The Launchpad, and The Runway) have the checks.

Launching a 181t vessel with Level2_LaunchPad (Max. 140t) on all 3 launchsites log checks:

// the Launchpad
[LOG 02:22:27.549] [Pre-Flight Check]: Checking for CraftWithinPartCountLimit: PASS!
[LOG 02:22:27.555] [Pre-Flight Check]: Checking for CraftWithinSizeLimits: PASS!
[LOG 02:22:27.565] [Pre-Flight Check]: Checking for CraftWithinMassLimits: FAIL!
[LOG 02:22:31.619] [Pre-Flight Check]: Launch Aborted.

// Woomerang
[LOG 02:22:45.995] [Pre-Flight Check]: Checking for CraftWithinPartCountLimit: PASS!
[LOG 02:22:45.997] [Pre-Flight Check]: Checking for CraftWithinSizeLimits: PASS!
[LOG 02:22:46.002] [Pre-Flight Check]: Checking for CraftWithinMassLimits: FAIL!
[LOG 02:22:48.766] [Pre-Flight Check]: Launch Aborted.

// Dessert
[LOG 02:24:54.956] [Pre-Flight Check]: Checking for CraftWithinPartCountLimit: PASS!
[LOG 02:24:54.957] [Pre-Flight Check]: Checking for ExperimentalPartsAvailable: PASS!
[LOG 02:24:54.959] [Pre-Flight Check]: Checking for CanAffordLaunchTest: PASS!
[LOG 02:24:54.961] [Pre-Flight Check]: Checking for NoControlSources: PASS!
[LOG 02:24:54.964] [Pre-Flight Check]: Checking for LaunchSiteClear: PASS!
[LOG 02:24:54.967] [Pre-Flight Check]: All Checks Complete. Go for Launch!

Since a player upgrades only the Launchpad and the Runways, it is make sense that increasing limitation doesn't propagate to other unchangeable launchsites and airfields.
On the other hand, in the VAB/SPH we see these mass limitation in the craft engineering log, and nothing tell us, that the mass is limited only for the Launchpad and not for other launchsites.

So:
Easy fix: make all checks the same (enable mass check on dessert objects);
Complex fix: leave mass check only for the Launchpad and the Runway, and make changes to the GUI for telling user about unlimited mass for other launchsites.
Hard fix: make all runways and launchsites independently upgradable (add their icons to the main KerbalSpaceCenter window, new models per level, and so on)