Though I haven't completed/posted on my immortal dynasty yet, I have spent some time doing some practice runs and planning in different towns and have some tips based on playing with some of the EPs, SPs, and Store Content that I thought I would share here:
1.Lucky Palms I have found that I love Lucky Palms, though I have just the standard version and not the gold version (no casino). I love it because of the space available, the many open lots, and the people. I have all EPs installed (except UL and Seasons) and even with the automagically installed lots (as well as a couple of EA built lots like the Movie Set from LN) there are still Dynasty lots available for play. Also, there are at least three available males that you can abuse use for dynasty purposes: Hendrix, Lennon, and Dreamer. Dreamer (I think it's Darren Dreamer, but I can't remember) is the easiest to woo and comes with lvl 7 painting and is single, but he also hates the outdoors and has a romantic interest. Lennon is in the culinary field, but I never got a shot to woo him with the celebrity system active (he's a lvl 4 celeb). But he's rich and has an expensive car. Hendrix is a last ditch effort and most difficult to woo because he's got commitment issues. However, he is also rich and comes with the most expensive car available.
I haven't tried with a male founder in Lucky Palms, yet. But I can tell you that the town itself is highly useful for the ID challenge. Also, there are no combined rabbit-holes, which makes it user-friendly for skill ops and career ops.
2.Preparation is Necessary So far, I have gone through a few tests of each town and played in them a lot after buying them to decipher bugs/glitches and find clues for a better game. By doing this, I've found that (while I love it) Hidden Springs would not be a great place for the ID challenge. I don't know about others, but I've found that Hidden Springs glitches by the Science facility, which sucks when trying to get collectibles. I have spent lots of time playing in all of the towns, and I've contemplated all of them for the challenge. While SV and Riverview might be best for the ID challenge thus far, I agree that they may take too many changes due to the automagically placed EP lots. Also, I always play a test game in each town when I get it so that I can learn who everyone is for potential mates and whatnot. I will pick a household to play, pause the game, learn each members' age, skills, LTW, traits, and other pertinent info (like career and zodiac) before entering edit town and changing houses. Another (somewhat easier but riskier) way to do this is to select "Choose Household" in a new town and read the bios for each house. It will at least give you an idea of what you can expect from each townie.
3.Sometimes less is more I love the new Seasons EP, and UL was fun the first week I played it. But, I removed them due to glitches and issues. I would love to play with them, but not while attempting my ID. Also, until the rules come out for UL in the ID challenge, I don't want to use it. I know that you can "turn off" your seasons and have perma-summer with Seasons, but I tried this in my first ID attempt and found that my sim was always complaining about the heat. So for now, I'm sticking to the tried and true EPs. Also, I have found that having fewer EPs and SPs helps with loading houses in my regular games.
4. Premium Content I love love love the Multitab for my typical games, especially since I always want my sims to max out all skills and the Multitab is perfect for that. However, I did have issues with my founder in my 2nd attempt of my ID because she kept autonomously listening to tabcasts for other skills that were set as future gens' supermax skills. And, if I moved away from her for a second to give her spouse (Darren Dreamer of Lucky Palms) a task, I'd typically come back to find her listening to fishing, logic, or whatever. Unless you are going to babysit your immortals every second of every day, skip the multitab and learn the skills manually. Also, the multitab messes with wish spams (as has been mentioned), and (in my experience) your sim may learn the skills too fast to spam ops. I've had Sims end up going through gardening, cooking, and fishing before without a single op coming through. What I do recommend with the multitab is to give it to your non-ID sims and have them quickly learn all of the necessary skills (cooking, gardening, and fishing) via the tabcasts while painting and sculpting. It's a fantastic tool for multitasking and getting so much done so fast.
The greenhouse content is also fab for all purposes, especially if you have Seasons installed. The reason is simple: if you add the roof sections on top of an existing roof of a greenhouse (ie build your greenhouse with a roof over it and add the sections afterward) you can actually garden inside the greenhouse without cheating. I also find the gardening station an absolute gem for so many reasons. First, it's so simple to fertilize every plant in its path. Take your fertilizers, drag them to the station, and then select "use composter" once it's full (three items). All of the plants will be fertilized and it will take so little actual fertilizer. Another nice use of it is to identify seeds. Quickly find out what kinds of special plants you have by identifying seeds with the station. One glitch I have found (the hard way) with this is that if you have too many seeds of the same kind you will actually lose them in the process. It will identify the seeds and then they will disappear. I lost many money tree seeds this way.
I haven't tried the harvest stand trick yet, but there may be something there. I'll have to try that out.
Lastly, the new Chicken Coop is a must have for quick cash in the beginning! I haven't used it on my ID file yet, but I did build a practice home and used it with fantastic results! Almost every day I found a rare exotic egg in the coop that was worth $1500. They start out this price, but it will drop throughout the day, so be sure to sell it soon after getting it. However, if you are attempting to get maximum LTHP, keep the egg in your inventory for a couple of hours as it adds a nice boost for holding the egg. (I think it was "Egg-static!" and around 20 or so mood points) But, it will go bad if left in your inventory at night, so use it for a couple of extra LTHP and then sell it for the money. To add to the rare egg, the eggs that come from the coop actually appear to increase in quality with each harvest. I've ended up with excellent quality eggs from the coop after four days of harvesting from it. Imagine what an excellent quality harvested egg could do if you planted it and grew the Egg plant.
I know that everyone has their own methods and tips, and I know this post is probably very lengthy, but this is what some of my research has uncovered that may be useful for others' ID attempts. I'm actually glad I took the time to research before starting my IDs.