I'm afraid you missing my Point, Mr Meow Meow Meow.... if I was trolling, you would be sure of it.
If you've never heard of Lufia 2, you should check it out. Many here will know that game well, and I mentioned it because it has a love triangle between the Hero, his best friend, and the female lead that the game's story is most remembered for. It is exceptionally well done. Plus, it's a classic that RPG fans should check out.
In terms of "mature relationships" I'm afraid you're going to eat crow on that one. I'm 26, married, and have 2 kids. The idea that "kissing" and "sex" makes me "uncomfortable" is beyond silly. I like them both actually....
I laughed at what you said for 2 reasons. 1 - it is rediculous to think of chibis being devious. 2 - stories usually develope the tension around the beginning of the relationship because it is frankly more exciting, more emotional, and beter charecter development. Kissing and having sex whenever throughout the story is almost never done in great pieces of literature for a reason.
Quite frankly, your last point is the correct one, as I said before. The problem is not the particular mechanics of a romance, but the WRITING. Love triangles, or sudden feeling of love, or whatever, is not the bad part. Cliche, even, is not bad. Poor writing is bad. If you're going to include romance (or any other major charecter-based mini-story) write it well. If you can't, don't waste your time. Great heroes with love for so-and-so female has been the main plot of many stories, and will continue to be for a long time. Many call this cliche, but whenever it is written well, it works. When you write, you cannot call something bad simply because it is predictable. You call something bad because it is not engaging, and many attempt to replace engaging with "everyone-likes-this-so-add-it" story. This is a bad idea.
I like romance in stories, if you can write it well, do it. If not, skip it.