To OP: I found out that you can get most of the classes (except ECM unfortunately which is the most grindy class in the game) to the top rank in relatively short time (about 2-3 weeks - add 50% for ECM). From my experience - and I was flying ALL ships in the game to find their strengths and weaknesses - Jeri tree is totally different from Empire one, it needs a different style of play. So unlocking cross faction is definitely no. Think about real life - you are learning to fly agile Su-35 and then you are going to fly stealth Raptor.
Basically I found just few ships that I would change as I couldn’t find any proper playstyle for them. So cross-tree unlocking is perfect as it is now - you can skip some ships. Looking at the Empire Intie line - you are talking about going from Tempest to Storm Viking. From the same point you have King Nibelung, Viking and Jarl, which are great ships. They can be built as anti-guard strike crafts, counter tackler or simply as dogfighters - is up to you. You can’t drain energy with them, but you can drain shields, slow ships, drop mines if someone is on your tail, sneak under the guard, suck his shields and plant a mine. You will love them.