yes, it is possible... however, it would be hard to start at that high a cap as there are very few players that can get you there. A typical single-season progressive has an average team salary of around $80m+/- depending on era. A dual season progressive is typically around $115m +/- depending on era(s), and a triple season progressive is typically around $140m +/-. I think the highest progressive salary I've ever seen in any league (triple era) was around $160m. So, capping at that level or above would be difficult unless your progressive used more than 3 seasons, or allowed drafting from a wider pool of player-seasons.

5 seasons out is not too many to plan for. It's a good start, but what happens after the 5th season? With a progressive you should think long term. 15-20 seasons +. I have two progressives I've started that are approaching their 28th and 26th seasons and two others that are around their 11th and 7th seasons (and 1 that is having its first draft next week). There's nothing wrong with planning ahead, in fact, it is probably helpful.