Anyone launching New TT would play to its obvious strengths, the main one of which is the ability to put a really nice layout on a reasonable sized board.
So the first product would be a basic layout and a well-known complete (probably DCC) train, possibly a small goods train in addition, with a (free!) slot together board in sections with the layout and maybe roads/ fields printed on it for easy laying.
Make it extremely pretty. Give it a great name. Big advertising budget. First train-set. Most first-time Dads wouldn't worry about there being nothing further available just yet in the scale. It would be hugely attractive just as a single purchase. Perfect scale for kids, fine enough scale for Dads.
Plenty of toy and model manufacturers market single project products. Wouldn't interest Hornby/Bachmann of course but I think it would sell.
The secret would be in giving very careful thought to the rail quality, gauge, profile, points, so that if it took off it could quickly become the basis for a super-detail follow-on using the same layout with extensions, sidings, whatever to draw in the modellers.
....because the scale is just so right.
Which: 1/100 or 1/120?