I do like your idea of SP being a Fel rule set shard, even a preTrammel shard. I think that would be great.
I like to see Devs working together with the Siege community about making Siege more like a Fel ruleset shard. I'm really not much for seeing Item Insurance on Siege, I rather saw a fix to the items and resources on Siege so it would be easier to replace them.
I can stock basic suits for casters and for warriors but the hard core PvM and PvP players build their suits to get max power and they all have their idea of how the suit should be. I can't stock a lot different set as Vendor fee will eat up my profit
One thing I really find make it hard is the 5 kind of resist on armor. They make it so hard to put a suit together. I guess it's to late to remove them but we could fix the problem if we add more basis resist to items so a suit crafted of colored resources would have 60-65 resist in each resist and looted magic items would have 50 to 62 resist after a crafter enhance it with colored resources. The new loot artifacts should have 50-62 resist without need for enhancing.
If they did that, the PvM'er could stock their vendors with better magic stuff from loot and the crafters could stock single armor pieces, like hat/helmets of different kind, some for casters and some for warriors and players could use vendor search to find the item with the mods they want without care about the resist. This way, we could keep looting and if not changed on Trammel shards it would keep the items balance vs Insurance there.
I also would have hard to give up the "vendor won't buy your wares" part of the ruleset as I believe it keep our economy good as less money are added to the game.
If we could make changes, that would draw more players to Siege, I would not mind to see recall and 7 char slots on the shard.
If Devs success it, it would be easy to make more Fel shards and as start, make a Fel copy of Atlantic included chars and houses.