And again we have a civilization linked to the new trade route/roads mechanic. Regarding, that you will normally have only a few trade routes available early in the game, instant roads are very strong, only in concerns for extra/easier movement and it is yet unknown if roads give a passive bonus like in CiV.
The only other civ so far I can imagine who can pump out a lot of roads a little bit later is England if it focus heavily on cities near the cost for their free Royal Dockyard. And until so far, the biggest sources of extra trade routes seem to be harbors and commercial hubs. With second, Germany might get a lot too because it wants to build a lot of ch to max their hanses.
In regards of the free trading post, as I have understood it, a trade post is constructed in each city you had already a trade route with. I think an important decision in the early game for a lot of other civs will be if they focus their limited trader units to build internal trade routes for their city connection or to establish trade routes to other civs/city states.
And the free trading post can be very potent. If you place three cities in a line, other civs might send a trader from city A to C passing through B to get the road going. But if they want the bonus of the trading post, they have to establish first a trade route to city B and then to city C. Rome can send it directly to C and already getting the bonus. Or even better, send a trade route from city A through B and C to some foreign City getting the bonus of two trade posts plus the benefit of that trade route itself. And until so far, that can be very good, does it seem that internal trade routes give mostly food and production bonus, but connection to other civs/city states give boni to gold, faith, culture, science depending on their districts. And when Egypt is the neighbor of Rome, you can even push your own city growth plus the gold advantage of your trade routes.
That will have a good synergy with the FREE bath districts. Probably you want to build them in every city and most city will be founded in the near of fresh water and mountains I think, so it is not that bad, that you will get a smaller housing bonus of it, but Bathes get a bonus to housing never the less and also amenities which will support a wide gameplay it think greatly. And until now, Im not sure if there are even special buildings for the aqueduct district at all, maybe sewers?
So considering that boni to amenities support wide gameplay, we have for expansive civs so far the Aztec (ULA, UB in entertainment district), Brazil (free entertainment district) and now Rome (free bathes). And considering the playstyle, they can be by now the fastest to establish a wide empire early on, maybe only contested by the Aztec depending on how good they can farm builders.
The Legion itself is strong as it is I think. Sure, other UU might have a bigger bonus, but a lot of them are very situational. The only concern I have is, that Legions probably need iron and I hope the lack of it will have changed compared to the Lets Plays of the Preview Press build.
They might not be that strong in the pure offense, but every civ without access to iron or horses and which dont have an other UU to counter it might have its problems to deal with it. The biggest advantage I think is, that it will be very hard to get rid of the advancement of the legions, because if they go in the defense, they can insta pop a fortress way earlier then most of the other civs (only china gets an earlier defense bonus with the great wall and only on its border edges). And I think most military advances wont just be Legions itself, they will probably supported by archers, catapults and maybe horses. The first both will greatly benefit from the defense bonus.
The only open point for me is still, how will legions and military engineers build roads? In the UI of the Legion there is symbol with a gear-wheel and an arrow. Might that be the button to construct roads? Maybe you have to draw a line like someone already mentioned? I personally dont think, that one road tile will need a whole charge, that would need quite a big amount of legions/military engineers to make actual use of it. Maybe it is a quarter of a charge, so you might lose the ability to build forts with a Legion who began to build roads. Or it will just need time (one tile per turn). But that might not prevent to mass spam roads in your territory like in old days (Civ 4 and prior). So it might be, that you maybe can only build roads between cities even with Legions/military engineers, but you can chose the path where it is going?
Still very uncertain about it and Im quite excited how Firaxis will handle it.