Gotta tell ya Dan, this doesn't look like a good idea. Historically you've been very reasonable about avoiding areas that encourage spending ubt, this isn't one of them.
Now we have a situation where we can stack 10x items but can only hold 5. The immediate assumption is "well I guess I have to buy the other 5 now" (cue the eye rolling)
The other less obvious choice that players will get to is having to go pick up items from their base area, leave, equip them and then come back for 5 more, which really just feels like a deliberate waste of my time.
Truthfully, I'm reluctant to even bring this up because i suspect your solution is to remove the "incentive" by reducing the stack limit to 5.. then we have 2 solutions to a problem that nobody but you had.
All of this is aside from the fact that I've already spent money to support this game and have 3 complete 10x runs ready to go in inventory. Now i have 2.5 so now what? Do i have to spend more, or did i spend too much? It looks to me like I've wasted literally Hundreds of ubt.