The main problem that you have with a band like TNT has got nothing to do with music, and everything to do with their name. For many-A&R men included-the only TNT that they remember is the 80's stuff, hence major record labels won't touch them with a barge pole as they have a kind of stigma attached to them. If they changed their name they would possibly have more success at attracting a major and all the publicity and airplay that goes with it.
However, for many even a name change cannot hide the fact that many members were associated with aor/melodic rock acts and this has the same effect...look at 40 Foot Ringo; courted by the major labels until they found out the Trixter association. Some have done it with success, for example Closure give little away when talking of their past credentials.
Shame really but that's the way it goes
Cock