Yak-130s would be tough due to Russia's wartime situation and the general environment of sanctions. Unlike Pakistan, I think Bangladesh is in a good place in terms of foreign and economic relations, especially with countries like South Korea. Best they keep that going and exact as many concessions, like manufacturing-related FDI and, potentially, tech-transfers for semiconductors and other critical industries. So, IMO, it'd be better for BD to avoid Russia, avoid China, and, frankly, avoid Pakistan (from a defense industry PoV).
As
@Oscar noted above, any fixed-wing fighter acquisition would be for neutralizing Myanmar. IMO, that should be a major priority for BD as they cannot afford to have two exposed flanks. Moreover, BD should start gradually flexing and expanding its writ into Arakan so as to settle the Rohingya issue once and for all.
In terms of India, they'll need to coordinate with Pakistan and procure from Turkiye. On the coordination front, there needs to be a plan in place to divide India's resources into a 3-way split: West (Pakistan), North (China), and East (BD).
Provided the West and North are active fronts, I don't think BD would have face the full brunt of India's might. Of course, this is contingent on Pakistan really stepping up as a credible land, air, and naval threat (the growth in the PN submarine fleet will be key).
For its part, however, I agree with you in that BD should be investing in mobile artillery as well as guided rocket and LACM/ASCM capabilities. They can acquire all of that off-the-shelf from Turkiye and, potentially, license manufacture the rockets. Furthermore, multi-layered and extensive IADS via PDMS+CIWS, MR-SAM, and LR-SAM (SIPER?) is key.
They have a good naval opportunity too... They ought to speak to ROK or Turkiye for new conventional submarines. In fact, that should be their primary naval focus, i.e., build a disproportionately large sub-surface fleet of ~1,500-ton SSKs, <500-ton SWATS, and a lot of UUV/AUVs. Station mobile ASCM launchers and SAMs by the coasts.
Basically, the idea should be to build enough to deny India access and control over the eastern flank. However, once that's achieved, build the capacity for offensive operations in concert with a western and/or northern advance. That's where something like the KF-21 would be key. This isn't to say any such outcome would happen, but India should be factoring it in as a real possibility in case it fights any one side.