Did a brief spreadsheet exercise in comparing my current 1000gp Irish warband to what I might have if I played Welsh with them instead.
With the Welsh inability to take armour and warhounds, I lose my current chieftain, three warriors with hand weapons, and two sets of warhounds, leaving me with 615gp worth of fighters after accounting for Welsh costs for warhorns, spears, and shields, but otherwise flush with 17 spears & shields; 6 javelin, HW & shield; 1 unarmoured spear & warhorn, and 2 unarmoured spears.
Obviously you can't play a warband without a chieftain, but outside of that I know I'd want to do a small contingent of bowmen if I were to build them further as Welsh. That would depend on me either replacing my current javelin guys (otherwise HW+shield) or adding more cheap spearmen to compensate, mind you.
And of course this is before accounting for talents. I might reprise the Hunters talent I typically use with my Irish, but then lies the question of what other talent I might include should I choose to go for a second one.