Ok, I tested it in Launch, Booster landing and ITS journey to Duna. I have some comments and suggestions.
1. Something weird with engines. When throttling is 0% it still provides thrust. First time i thought it is kraken increases velocity In order to stop it, I had to shut down engine manually. Also central cluster of booster swithces off only 1 of 7 engines via action groups and I had to stwich others manually. It was difficult to land, because that buggy thrust TWR on Duna is more than 1, when ITS is almost dry!
2. Difficult to point grid fins. Seems to me they dont work.
3. I thinks there should not be a reaction wheel on the booster, and probably in ITS (but it more for RSS players). And we need more powerful RCS thruster on top of booster.
4. ITS central landing engines do not have yaw animation (may be yaw at all, I forgot to check it) and usually explodes when Vac engines work.
5. When I entered Duna atmosphere on 5300 m/s (80 days travel, right? On Kerbin orbit boost impulse was about 2200 m/s) with PE at 25 km, first exploded landing gear (roll was at 0 degree) and the ITS itslef :(. May be on RSS with Mars it will not be so taugh. So to land on Duna I cheated with temperature ignore button and aerobrake worked only with 14 km PE, higher PE is not enough to slow down ITS.
6. There is no landing gear restraction animation, only deploying.
7. I would suggest to make heat shielding as a separate part with ablator points. I ussualy play with Kerbal construction time, which provides opportuinity to make realy reusable crafts. Without separate shielding there is no way to replace parts, only replacing the whole spaceship instead of reuse.
Hope you will fix everything and make really great mod I think the first thing should be fixed is bug with engines.
What is gonna be with cargo bay?