It seems pretty clear to me that the Ideals aren't as fast and simple as a video game level-up. It's important to think about what's going on here from thematic and character perspectives.
The Nahel bond is the combination of the influence of two different Shards, Honor and Cultivation, and reflects their specific intents. Honor is all about binding oaths, while Cultivation is the Shard of curated growth. We've seen their limitations highlighted before - some have said that Honor was more concerned about oaths being made and kept regardless of the substance of those oaths, while a similar criticism of Cultivation is that she seems to prioritize growth and abundance for their own sake. Combined together, however, their influence involves empowering mortals who make and keep oaths, which are in turn formulated specifically to facilitate their emotional and spiritual growth.
Nale is a pretty perfect example of the point I'm striving at, here - he has apparently progressed sufficiently through the Ideals to have ascended to the Fifth Ideal, but that hasn't prevented him from spearheading a pretty horrific and monstrous agenda. His killing of countless nascent surgebinders apparently doesn't conflict with his oaths (including the most foundational "life before death" of the First Ideal), because the Skybreakers interpret that oath so very, very differently from, say, our Windrunners.
The various Orders diverge pretty dramatically beyond the First Ideal, and even differ greatly in terms of which actions they intuit as following naturally from the shared First Ideal. The different Orders bond with different kinds of spren, gain different surgebinding abilities, and swear different oaths after the first. We also have pretty stark evidence that even within the same order, the oaths can take slightly different forms depending on the personal interpretation and the spiritual needs of the individual swearing them - see how Teft's version of the Windrunner oaths differ from Kaladin's. Kaladin wasn't even aware of the specific wording of the First Ideal until he had progressed very nearly to the Second Ideal of the Windrunners, but that didn't slow his progress, because he had already sworn himself to a code of behavior that aligned with those ideals.
All this is to point out that all the evidence suggests a huge amount of variance between different orders and even individuals as they progress through the Nahel bond. WoB confirms that different Orders gain access to different surges and benefits of the bond at different points during their journey. It seems pretty obvious that the Windrunner path involves a Shardblade at the Third ideal and plate at the Fourth, but Shallan obviously got access to a Shardblade much earlier and it's very possible that Dalinar won't ever gain access to a Shardblade simply because of the specific personality of the Stormfather that he has bonded with.
While it's probably true that some kind of increase in power is going to be associated with ascending to the Fifth Ideal, I very much suspect that what happens at that point is going to vary pretty widely across orders and maybe even based on individual needs within the same order.
