Make Tyrell’s playable again

Also hereditary high stewards were not low status castellans, the Stewarts/Stuart's of Scotland, who the Tyrells are probably based on, were some of the largest landowners in Scotland before they became kings, the position of Lord High Steward of England was first held by the earls of Leicester and has been held by various dukes for most of its history, the Grand Master of France (the French equivalent of high steward) was usually held by the Princes of Condé. Even in ASOIAF is clear that stewards are not just random landed knights, Erik Ironmaker, Steward of the Iron Islands for example. The notion that the Tyrell's were insignificant is Florent self aggrandisement, the WOIAF has the Tyrells serving to settle disputes, and serving as loyal stewards for a couple of thousand years for the Gardeners. The previous set up of them being lords not high lords, like the Florent was a good representation of how the florents were slightly more powerful in terms of land and men but the Tyrells had the ear of the Gardeners

They married the daughter of gardener kings on 10 separate occasions and ruled the reach in all but name as regents and wartime castillans on multiple occasions according to WOIAF, suggesting a certain level of power and prestige, and even if you go with the argument that they didn't hold the title of Lord, in the game currently the Sers of New Barrel, Ser Davos, House Cassel of Kings Course, and the Sers of Ninestars all hold provinces despite being landed knights not lords. You could very easily give inchfield back to the Tyrells, like it was in 1.7, as the merryweathers also hold longtable and I don't think there's any evidence of them holding inchfield.

Also if you didn't want to do that you could fairly easily give them a province in a different way - one easy fix is giving the Peakes an extra BARONY (a castle is a castle after all) and then making the Tyrells lords of Yelshire (currently held by the Peakes). Or do something similar with the Osgreys and replace one of their four counties with a barony and give the Tyrells a county. It just seems a shame to completely wall off the Tyrells in early bookmarks and submods, especially when so many reach houses have 2-3 provinces 

Reach has a problem with too many houses and too few provinces. Merryweathers were quite powerful once hence why they hold Inchfield. Personally, I would give them some duchy instead, but there are other people who have different opinion on the matter. Osgreys canonically once held four castles (no mention if Leafy Lake was one of those four) so there's that.

I thought about making Osgrey's fourth castle a Leafy Lake, therefore freeing one county, but that probably would require further discussion on the topic. Inchfield by the way should be held by Inchfields all the time if all was well. And Tyrells lost county to Balls, not Inchfields. Since Balls are descending from Garth the Green, it's rather certain that they should be holding some province. Declining buildings doesn't really lower house's prestige and power much. I would really preffer if Merryweathers were dukes, but at the moment we haven't done anything about them, although we have some ideas and hopefully we will manage to do something eventually.
Just to be clear, it wasn't my decision to reduce Tyrells to barons. I would be ok if they held county but since Reach is so overcrowded it seems tricky to do at the moment.