New printer thoughts

I have been in the sign business for less than a year. My focus is on smaller signage and banners. In the near future, I am going to need a new printer, so I'd like some insight from you guys.

From a prior business, I have an HP DesignJet 5500 42" dye. I have a huge seasonal business that requires lots of 36"-42" posters. This machine is blazing fast (300+ sf/hour), but since it is dye, I am limited to using it for indoor jobs. Plus it is only 42" long. These posters I mentioned are going to need to be bigger.

For outdoor I have a Falcon Outdoor Jr. 36". This machine sucks! It is slow, and I spend all my time trying to maintain it. But this is my only outdoor/ecosolvent machine.

I need something bigger than 42" for the posters, so I might as well upgrade the outdoor printer at the same time.

I would like your thoughts on the following...
1. For the sign shop aspect of things, I assume 48" would be the minimum to consider. Is there much reason to look at 54" or 60"?
2. Type of printer for long term use? Latex, eco solvent, etc?
3. Which brand(s) are considered to be the Cadillac vs. the others? I guess Mimaki, Mutoh, Epson are the main ones. Are any of them generally more user friendly than others?
4. I have gotten spoiled with the low ink cost for my HP. I need a machine that has affordable ink. And is fast too.

I know there are a lot of variables here. I want to spend around $15K on the project. Any thoughts would be appreciated.