Good show guys and @keeegs, welcome mate!!
Loved the ideas so much, I suddenly got inspired with one toward show's end.
Since you invited idea-sharing, here it is (please please please correct whatever I have wrong here, as I may have the odd detail misunderstood :)):

Can Gladiator cards be used in:

• Frontier format? No.
• Modern format? Yes. Gladiator cards can be used, but the longer a player stays with Splinterlands the less likely they are to engage in Modern format. Recent times have seen the numbers of people engaging in Modern format having declined.
• Wild format? Yes. Gladiator cards can of course be used in Wild, but your highest-level card is what will be used in battle, leaving your excess cards without use there.
• Survival mode? Yes, in fact, excess Gladiator cards are mostly find their utility here, but for those who wish not to engage in playing survival mode there appears at this time no other outlet to utilise excess cards apart from burning them for more merits.

If you have both a Standard as well as a Gold version of a card, then you could alternate between playing Gold frays and Standard frays in your guild, so there is this utility, but apart from that, Gladiator cards have limited utility in comparison to other cards in the game. Even soulbound cards can become unlocked and rented or sold in the marketplace, opening their useability up to being placed on land, mage wagons, etc, gladiator cards cannot be used on wagons (but can be placed on land, so that is a big plus). I'm one of the players that has no current desire to engage in land, so for me this is not an option.

My idea is that when a player’s account maxes out a Gladiator card, other cards accrued after that point can become unlocked/unbound and placed on the market, to the cost of an unbinding fee, much like soulbound cards are.
This would bring about the useability of gladiator cards for all Splinterlands players, even if they’ve not engaged in a guild and never will.
I suppose though, that this limits some of the incentive to join a guild and engage in guild brawls, HOWEVER, it actually might create incentive to join a guild.
Since sale prices of Gladiator cards may fetch valuable prices due to their power, time investment to acquire them, more time and attention of players might move toward guilds in order to accumulate Gladiator cards without having to pay for them.
Having these cards on the market may in fact bring more attention to them to new and existing players.

So how would Gladiator cards be used by players who aren’t even involved in guild brawls?
Well, for those who are invested in the Modern format, putting money towards the use of a Gladiator card is a possibility, for whenever the ruleset may arise where a Gladiator may be summoned.
However, this is far less common of a function of Gladiator cards.
The cards would be utilised in Survival and Wild formats and so for these players, the added incentive to buy or rent summoners that can summon a Gladiator card, such as Helios Matriarch, might then exist, stimulating the ecosystem’s economy even more.
In fact, this player hopes that new summoners will emerge in future card sets that can summoner Gladiator cards, which came about through the Chaos Legion soulbound reward card set.
Players’ newly-purchased or rented Gladiator card(s) could them be put to further use in these formats.

What do you think @giotrix @mattclarke @bobaphet and @keeegs?

Cheers,
Guyman