The timeline is correct but the model numbers are wrong for the LB 10-X to seriously be in the running in my opinion. It seems more likely the Mk. V was either simply not used for whatever reason (marketing having a hand here...) or a pure testbed leading into the Mk. VI.
Agreed on the LBX timeline, its a shame too, I thought 3x LB10 made for a nasty option in all honesty. The PPC is probably a more likely option.
Did a little tinkering and an there is room for the following options...
1. ICE + AC5 x3
2. SFE + AC10 x3 (Loss of Armor)
3. SFE + PPC x3 (Loss of Armor)
4. SFE + LL x3
5. SFE (2/3) and Gauss x2
6. ICE + Gauss x3 (Loss of Armor)
So I see a few ways they could go but I think only the Mk1-2 could use ICE/SFE because w/ the 3, 4, & 6 all being XL I would assume that the 5 is also, so in that case only the PPC makes any sense really.