I'm not what you would call an expert, but here's my two cents.
First, I use my Elan as my daily driver. I feel like anything else would be like buying your little girl that special Barbie she wants, then telling her she can't play with it because it will lose its value. The Elan is just too good on the road, and too much fun to drive. The Isuzu drivetrain is pretty much bulletproof, as long as you take reasonable care of it, like any other car. I had an Isuzu Impulse (same engine and tranny, and Lotus "tuned" suspension) for almost ten years, and it was 100% reliable. I have every confidence in my Elan's mechanics. The Elan has plenty of quirks, but that's what makes it special.
Second. Watch out for a car that has been at the beach for a long time, just like one that has been up North. You definitely want to carefully inspect it underneath. (Mine was a northern car, and I have to replace the wishbones due to rust) You've made the right move asking for help here before buying. That silver car you mentioned is in a thread on here in the U.S. Elans - For Sale section
(here). You can get a lot of good info there. If it's the one I'm thinking of, it belongs to an LEC member.
Third. Based on what I've read, having never driven one myself, an Elise would probably not be as good a daily driver as an Elan, because the Elan is more comfortable. Oh, and an Elan will turn just as many heads, in case you're wondering.
Simple answer to your question: Yes. You can certainly use an Elan as a daily driver.