I actually really like the support system in RD. Having duel Earth affinities is cheap as all hell up until the final bosses of the game where it's useless. I can understand why people prefer the other support system since it builds character but most of the characters already got that in PoR and the ones that didn't just get the short end of the stick. Another problem with the support system is how bias some of the affinities are. As I said, Earth is practically broken since having 1 at A rank can get you +30 avoid and having 2 gets you +45 avoid! While Wind gets you a little bit of avoid and hit and Heaven gets you a lot of hit and pretty much every character that has Heaven, doesn't need it.
I also really enjoy the alternation between Micaiah's group in part 1, to Elincia's in part 2, back to Micaiah's a bit and adding Ike in part 3 and finally part 4 has everyone. It makes you have to respect characters you'd otherwise quickly abandon. Why use Zihark when Mia starts at a higher level, fights higher leveled enemies and doesn't have to deal with the high accuracy laguz? Because Zihark is one of the best units Micaiah's team gets access to. Granted, you can send him over to Ike's side which is really useful if you plan on bringing him to the endgame or if you just want to make Micaiah's chapters in part 3 more difficult.
I also love how exploitable the shifting around of characters can be in that game. Give Ilyana the Brave Sword before endgame of part 1 and you can have Mia or Ike use it in part 3. Give the Brave Lance to Marcia in chapter 3 (I think) part 2 and you can then give it to Haar who can then proceed to give it to anyone on Ike's team. Later, in part 3 you can do the same thing with Jill and/or Zihark.
There's also a good amount of exploitable grinding for anyone who wants to make use of it. Laura is easy to grind with at the beginning with any enemy that stays still and Micaiah can grind with her with Sacrifice. Micaiah, Ilyana and Laura at 2nd tier can grind on any priests, especially if you have Nailah Glare them. That prison level in part 1 is really good for grinding ESPECIALLY for Muarim and Vika. Endgame of part 1 is similar with Jarod. Heather can get to level 20 Whisper in part 2 thanks to an exploit in enemy Rogue ai along with stealing. The biggest exploit and the one I use the most is Unforgivable Sin, the final chapter before the endgame of part 4. A large amount of spawning laguz (not infinite) that give high exp and a good starting defensive position. You can put most units on Hawk Army and thanks to the way the convoy works, you can have any skill and any weapons you want at that point, plus you should have enough gold to buy whatever you may need. On my current playthrough, I got Aran from level 13 Halberdier to level 9 Sentinel and I'm not even done that chapter yet!
Sorry for what is essentially a 'blog' in regards to RD rather than Ike in Sm4sh ^^; I nerd the **** out waaaay too much when it comes to RD.