I'm stuck between army ideas, and would love some insight from other hobbyists

So, I've been getting really into Horus Heresy 3.0, and I've been working on my main Traitor Ultramarine army as my main focus, but I know myself too well to know im already looking ahead at what could be the next thing on the chopping block.

With that in mind ive been list building and list building and have settled on a handful of ideas id love to do, but im struggling to choose one that feels just right

The options I have are:

. Alpha Legion - i have enough bits given to me by a friend to make a solid start on this force. I enjoy their tactical covertness and their gameplay of prioritising Assassinations of Command and High Command units. Also, Alpharius is a sick model id love to play with, though I preferred his 2.0 rules, ill still run him regardless as a good bit of fun

. Siege of Terra Blood Angels - using the Blackshields Ruleset with Reaper of Lives and Eternal Vendetta to represent the moment where Blood Angels became barbarians in their Black Rage that came with the death of their primarch, Sanguinius. I would use a small allied force of Custodian Guard to add to the narrative idea of the Siege. This feels very fun, or if I was to go full swing into Blood Angels and maybe bring Sanguinius, though im a little apprehensive of bringing 40 assault marines so one of Sanguinius' abilities actually apply (i think it gives each of those squads a prime benefit, so id be stacking Revenants)

. Luna Wolves - this is the idea that brings me here. Im rereading Horus Rising with the new publications of the heresy books, and I'm enjoying rereading about Loken and Tarrik, Abaddon, Maloghurst, the whole Mournival. I made a list that feels very thematic and tactically sound, and as the friend ill mainly be playing against wants to do loyalist Emperor's Children, we'd both be giddy to have Loken and Lucius duke it out on tabletop.

All of these ideas have merit to them, with alpha legion being immediately possible, but its the toss up between Blood Angels and Luna Wolves right now.

In the future, me and my friend aim to make a Zone Mortalis board and do multiple small armies to play games and add our roleplay ontop of it, taking part as the characters we create, and live out our heresy pipe dreams

This is for the future, and ive already got ideas of what I can do, but for a next army project, its these ive proposed here. Also, it means I can play games against myself, which is how ive learned to play 3.0 thus far, so I thought id reach out and ask for people's advice on making a decision, and I welcome out of the box thinking

If it helps, at minimum, looking at 1.5k - 3k points.